Add new MIR constant propagation based on dataflow analysis

The current constant propagation in `rustc_mir_transform/src/const_prop.rs` fails to handle many cases that would be expected from a constant propagation optimization. For example:
```rust
let x = if true { 0 } else { 0 };
```
This pull request adds a new constant propagation MIR optimization pass based on the existing dataflow analysis framework. Since most of the analysis is not unique to constant propagation, a generic framework has been extracted. It works on top of the existing framework and could be reused for other optimzations.

Closes #80038. Closes #81605.

## Todo
### Essential
- [x] [Writes to inactive enum variants](rust-lang/rust#101168 (review)). Resolved by rejecting the registration of places with downcast projections for now. Could be improved by flooding other variants if mutable access to a variant is observed.
- [X] Handle [`StatementKind::CopyNonOverlapping`](rust-lang/rust#101168 (comment)). Resolved by flooding the destination.
- [x] Handle `UnsafeCell` / `!Freeze` correctly.
- [X] Overflow propagation of `CheckedBinaryOp`: Decided to not propagate if overflow flag is `true` (`false` will still be propagated)
- [x] More documentation in general.
- [x] Arguments for correctness, documentation of necessary assumptions.
- [x] Better performance, or alternatively, require `-Zmir-opt-level=3` for now.

### Extra
- [x]  Add explicit unreachability, i.e. upgrading the lattice from $\mathbb{P} \to \mathbb{V}$ to $\set{\bot} \cup (\mathbb{P} \to \mathbb{V})$.
- [x] Use storage statements to improve precision.
- [ ] Consider opening issue for duplicate diagnostics: rust-lang/rust#101168 (comment)
- [ ] Flood moved-from places with $\bot$ (requires some changes for places with tracked projections).
- [ ] Add downcast projections back in.
- [ ] [Algebraic simplifications](rust-lang/rust#101168 (comment)) (possibly with a shared API; done by old const prop).
- [ ] Propagation through slices / arrays.
- [ ] Find other optimizations that are done by old `const_prop.rs`, but not by this one.

Pkgsrc changes:
 * Adjust patches and cargo checksums to new versions,
   but also one strange "mips" conditional.

Upstream changes:

Version 1.67.0 (2023-01-26)
==========================

Language
--------

- [Make `Sized` predicates coinductive, allowing cycles.]
  (rust-lang/rust#100386)
- [`#[must_use]` annotations on `async fn` also affect the
  `Future::Output`.] (rust-lang/rust#100633)
- [Elaborate supertrait obligations when deducing closure signatures.]
  (rust-lang/rust#101834)
- [Invalid literals are no longer an error under `cfg(FALSE)`.]
  (rust-lang/rust#102944)
- [Unreserve braced enum variants in value namespace.]
  (rust-lang/rust#103578)

Compiler
--------

- [Enable varargs support for calling conventions other than `C`
  or `cdecl`.] (rust-lang/rust#97971)
- [Add new MIR constant propagation based on dataflow analysis.]
  (rust-lang/rust#101168)
- [Optimize field ordering by grouping m\*2^n-sized fields with
  equivalently aligned ones.] (rust-lang/rust#102750)
- [Stabilize native library modifier `verbatim`.]
  (rust-lang/rust#104360)

Added and removed targets:

- [Add a tier 3 target for PowerPC on AIX]
  (rust-lang/rust#102293), `powerpc64-ibm-aix`.
- [Add a tier 3 target for the Sony PlayStation 1]
  (rust-lang/rust#102689), `mipsel-sony-psx`.
- [Add tier 3 `no_std` targets for the QNX Neutrino RTOS]
  (rust-lang/rust#102701),
  `aarch64-unknown-nto-qnx710` and `x86_64-pc-nto-qnx710`.
- [Remove tier 3 `linuxkernel` targets]
  (rust-lang/rust#104015) (not used by the
  actual kernel).

Refer to Rust's [platform support page][platform-support-doc]
for more information on Rust's tiered platform support.

Libraries
---------

- [Merge `crossbeam-channel` into `std::sync::mpsc`.]
  (rust-lang/rust#93563)
- [Fix inconsistent rounding of 0.5 when formatted to 0 decimal places.]
  (rust-lang/rust#102935)
- [Derive `Eq` and `Hash` for `ControlFlow`.]
  (rust-lang/rust#103084)
- [Don't build `compiler_builtins` with `-C panic=abort`.]
  (rust-lang/rust#103786)

Stabilized APIs
---------------

- [`{integer}::checked_ilog`]
  (https://doc.rust-lang.org/stable/std/primitive.i32.html#method.checked_ilog)
- [`{integer}::checked_ilog2`]
  (https://doc.rust-lang.org/stable/std/primitive.i32.html#method.checked_ilog2)
- [`{integer}::checked_ilog10`]
  (https://doc.rust-lang.org/stable/std/primitive.i32.html#method.checked_ilog10)
- [`{integer}::ilog`]
  (https://doc.rust-lang.org/stable/std/primitive.i32.html#method.ilog)
- [`{integer}::ilog2`]
  (https://doc.rust-lang.org/stable/std/primitive.i32.html#method.ilog2)
- [`{integer}::ilog10`]
  (https://doc.rust-lang.org/stable/std/primitive.i32.html#method.ilog10)
- [`NonZeroU*::ilog2`]
  (https://doc.rust-lang.org/stable/std/num/struct.NonZeroU32.html#method.ilog2)
- [`NonZeroU*::ilog10`]
  (https://doc.rust-lang.org/stable/std/num/struct.NonZeroU32.html#method.ilog10)
- [`NonZero*::BITS`]
  (https://doc.rust-lang.org/stable/std/num/struct.NonZeroU32.html#associatedconstant.BITS)

These APIs are now stable in const contexts:

- [`char::from_u32`]
  (https://doc.rust-lang.org/stable/std/primitive.char.html#method.from_u32)
- [`char::from_digit`]
  (https://doc.rust-lang.org/stable/std/primitive.char.html#method.from_digit)
- [`char::to_digit`]
  (https://doc.rust-lang.org/stable/std/primitive.char.html#method.to_digit)
- [`core::char::from_u32`]
  (https://doc.rust-lang.org/stable/core/char/fn.from_u32.html)
- [`core::char::from_digit`]
  (https://doc.rust-lang.org/stable/core/char/fn.from_digit.html)

Compatibility Notes
-------------------

- [The layout of `repr(Rust)` types now groups m\*2^n-sized fields
  with equivalently aligned ones.]
  (rust-lang/rust#102750) This is intended
  to be an optimization, but it is also known to increase type
  sizes in a few cases for the placement of enum tags. As a reminder,
  the layout of `repr(Rust)` types is an implementation detail,
  subject to change.
- [0.5 now rounds to 0 when formatted to 0 decimal places.]
  (rust-lang/rust#102935)
  This makes it consistent with the rest of floating point formatting that
  rounds ties toward even digits.
- [Chains of `&&` and `||` will now drop temporaries from their
  sub-expressions in evaluation order, left-to-right.]
  (rust-lang/rust#103293) Previously, it
  was "twisted" such that the _first_ expression dropped its
  temporaries _last_, after all of the other expressions dropped
  in order.
- [Underscore suffixes on string literals are now a hard error.]
  (rust-lang/rust#103914)
  This has been a future-compatibility warning since 1.20.0.
- [Stop passing `-export-dynamic` to `wasm-ld`.]
  (rust-lang/rust#105405)
- [`main` is now mangled as `__main_void` on `wasm32-wasi`.]
  (rust-lang/rust#105468)
- [Cargo now emits an error if there are multiple registries in
  the configuration with the same index URL.]
  (rust-lang/cargo#10592)

Internal Changes
----------------

These changes do not affect any public interfaces of Rust, but they
represent significant improvements to the performance or internals
of rustc and related tools.

- [Rewrite LLVM's archive writer in Rust.]
  (rust-lang/rust#97485)

Pkgsrc changes:
 * Adjust patches (add & remove) and cargo checksums to new versions.
 * It's conceivable that the workaround for LLVM based NetBSD works
   even less in this version (ref. PKGSRC_HAVE_LIBCPP not having a
   corresponding patch anymore).

Upstream changes:

Version 1.68.2 (2023-03-28)
===========================

- [Update the GitHub RSA host key bundled within Cargo]
  (rust-lang/cargo#11883).
  The key was [rotated by GitHub]
  (https://github.blog/2023-03-23-we-updated-our-rsa-ssh-host-key/)
  on 2023-03-24 after the old one leaked.
- [Mark the old GitHub RSA host key as revoked]
  (rust-lang/cargo#11889).
  This will prevent Cargo from accepting the leaked key even when
  trusted by the system.
- [Add support for `@revoked` and a better error message for
  `@cert-authority` in Cargo's SSH host key verification]
  (rust-lang/cargo#11635)

Version 1.68.1 (2023-03-23)
===========================

- [Fix miscompilation in produced Windows MSVC artifacts]
  (rust-lang/rust#109094)
  This was introduced by enabling ThinLTO for the distributed rustc
  which led to miscompilations in the resulting binary. Currently
  this is believed to be limited to the -Zdylib-lto flag used for
  rustc compilation, rather than a general bug in ThinLTO, so only
  rustc artifacts should be affected.
- [Fix --enable-local-rust builds]
  (rust-lang/rust#109111)
- [Treat `$prefix-clang` as `clang` in linker detection code]
  (rust-lang/rust#109156)
- [Fix panic in compiler code]
  (rust-lang/rust#108162)

Version 1.68.0 (2023-03-09)
===========================

Language
--------

- [Stabilize default_alloc_error_handler]
  (rust-lang/rust#102318)
  This allows usage of `alloc` on stable without requiring the
  definition of a handler for allocation failure. Defining custom
  handlers is still unstable.
- [Stabilize `efiapi` calling convention.]
  (rust-lang/rust#105795)
- [Remove implicit promotion for types with drop glue]
  (rust-lang/rust#105085)

Compiler
--------

- [Change `bindings_with_variant_name` to deny-by-default]
  (rust-lang/rust#104154)
- [Allow .. to be parsed as let initializer]
  (rust-lang/rust#105701)
- [Add `armv7-sony-vita-newlibeabihf` as a tier 3 target]
  (rust-lang/rust#105712)
- [Always check alignment during compile-time const evaluation]
  (rust-lang/rust#104616)
- [Disable "split dwarf inlining" by default.]
  (rust-lang/rust#106709)
- [Add vendor to Fuchsia's target triple]
  (rust-lang/rust#106429)
- [Enable sanitizers for s390x-linux]
  (rust-lang/rust#107127)

Libraries
---------

- [Loosen the bound on the Debug implementation of Weak.]
  (rust-lang/rust#90291)
- [Make `std::task::Context` !Send and !Sync]
  (rust-lang/rust#95985)
- [PhantomData layout guarantees]
  (rust-lang/rust#104081)
- [Don't derive Debug for `OnceWith` & `RepeatWith`]
  (rust-lang/rust#104163)
- [Implement DerefMut for PathBuf]
  (rust-lang/rust#105018)
- [Add O(1) `Vec -> VecDeque` conversion guarantee]
  (rust-lang/rust#105128)
- [Leak amplification for peek_mut() to ensure BinaryHeap's invariant
  is always met]
  (rust-lang/rust#105851)

Stabilized APIs
---------------

- [`{core,std}::pin::pin!`]
  (https://doc.rust-lang.org/stable/std/pin/macro.pin.html)
- [`impl From<bool> for {f32,f64}`]
  (https://doc.rust-lang.org/stable/std/primitive.f32.html#impl-From%3Cbool%3E-for-f32)
- [`std::path::MAIN_SEPARATOR_STR`]
  (https://doc.rust-lang.org/stable/std/path/constant.MAIN_SEPARATOR_STR.html)
- [`impl DerefMut for PathBuf`]
  (https://doc.rust-lang.org/stable/std/path/struct.PathBuf.html#impl-DerefMut-for-PathBuf)

These APIs are now stable in const contexts:

- [`VecDeque::new`]
  (https://doc.rust-lang.org/stable/std/collections/struct.VecDeque.html#method.new)

Cargo
-----

- [Stabilize sparse registry support for crates.io]
  (rust-lang/cargo#11224)
- [`cargo build --verbose` tells you more about why it recompiles.]
  (rust-lang/cargo#11407)
- [Show progress of crates.io index update even `net.git-fetch-with-cli`
  option enabled]
  (rust-lang/cargo#11579)

Misc
----

Compatibility Notes
-------------------

- [Add `SEMICOLON_IN_EXPRESSIONS_FROM_MACROS` to future-incompat report]
  (rust-lang/rust#103418)
- [Only specify `--target` by default for `-Zgcc-ld=lld` on wasm]
  (rust-lang/rust#101792)
- [Bump `IMPLIED_BOUNDS_ENTAILMENT` to Deny + ReportNow]
  (rust-lang/rust#106465)
- [`std::task::Context` no longer implements Send and Sync]
  (rust-lang/rust#95985)

nternal Changes
----------------

These changes do not affect any public interfaces of Rust, but they represent
significant improvements to the performance or internals of rustc and related
tools.

- [Encode spans relative to the enclosing item]
  (rust-lang/rust#84762)
- [Don't normalize in AstConv]
  (rust-lang/rust#101947)
- [Find the right lower bound region in the scenario of partial order relations]
  (rust-lang/rust#104765)
- [Fix impl block in const expr]
  (rust-lang/rust#104889)
- [Check ADT fields for copy implementations considering regions]
  (rust-lang/rust#105102)
- [rustdoc: simplify JS search routine by not messing with lev distance]
  (rust-lang/rust#105796)
- [Enable ThinLTO for rustc on `x86_64-pc-windows-msvc`]
  (rust-lang/rust#103591)
- [Enable ThinLTO for rustc on `x86_64-apple-darwin`]
  (rust-lang/rust#103647)

Version 1.67.0 (2023-01-26)
==========================

Language
--------

- [Make `Sized` predicates coinductive, allowing cycles.]
  (rust-lang/rust#100386)
- [`#[must_use]` annotations on `async fn` also affect the
  `Future::Output`.] (rust-lang/rust#100633)
- [Elaborate supertrait obligations when deducing closure signatures.]
  (rust-lang/rust#101834)
- [Invalid literals are no longer an error under `cfg(FALSE)`.]
  (rust-lang/rust#102944)
- [Unreserve braced enum variants in value namespace.]
  (rust-lang/rust#103578)

Compiler
--------

- [Enable varargs support for calling conventions other than `C`
  or `cdecl`.] (rust-lang/rust#97971)
- [Add new MIR constant propagation based on dataflow analysis.]
  (rust-lang/rust#101168)
- [Optimize field ordering by grouping m\*2^n-sized fields with
  equivalently aligned ones.] (rust-lang/rust#102750)
- [Stabilize native library modifier `verbatim`.]
  (rust-lang/rust#104360)

Added and removed targets:

- [Add a tier 3 target for PowerPC on AIX]
  (rust-lang/rust#102293), `powerpc64-ibm-aix`.
- [Add a tier 3 target for the Sony PlayStation 1]
  (rust-lang/rust#102689), `mipsel-sony-psx`.
- [Add tier 3 `no_std` targets for the QNX Neutrino RTOS]
  (rust-lang/rust#102701),
  `aarch64-unknown-nto-qnx710` and `x86_64-pc-nto-qnx710`.
- [Remove tier 3 `linuxkernel` targets]
  (rust-lang/rust#104015) (not used by the
  actual kernel).

Refer to Rust's [platform support page][platform-support-doc]
for more information on Rust's tiered platform support.

Libraries
---------

- [Merge `crossbeam-channel` into `std::sync::mpsc`.]
  (rust-lang/rust#93563)
- [Fix inconsistent rounding of 0.5 when formatted to 0 decimal places.]
  (rust-lang/rust#102935)
- [Derive `Eq` and `Hash` for `ControlFlow`.]
  (rust-lang/rust#103084)
- [Don't build `compiler_builtins` with `-C panic=abort`.]
  (rust-lang/rust#103786)

Stabilized APIs
---------------

- [`{integer}::checked_ilog`]
  (https://doc.rust-lang.org/stable/std/primitive.i32.html#method.checked_ilog)
- [`{integer}::checked_ilog2`]
  (https://doc.rust-lang.org/stable/std/primitive.i32.html#method.checked_ilog2)
- [`{integer}::checked_ilog10`]
  (https://doc.rust-lang.org/stable/std/primitive.i32.html#method.checked_ilog10)
- [`{integer}::ilog`]
  (https://doc.rust-lang.org/stable/std/primitive.i32.html#method.ilog)
- [`{integer}::ilog2`]
  (https://doc.rust-lang.org/stable/std/primitive.i32.html#method.ilog2)
- [`{integer}::ilog10`]
  (https://doc.rust-lang.org/stable/std/primitive.i32.html#method.ilog10)
- [`NonZeroU*::ilog2`]
  (https://doc.rust-lang.org/stable/std/num/struct.NonZeroU32.html#method.ilog2)
- [`NonZeroU*::ilog10`]
  (https://doc.rust-lang.org/stable/std/num/struct.NonZeroU32.html#method.ilog10)
- [`NonZero*::BITS`]
  (https://doc.rust-lang.org/stable/std/num/struct.NonZeroU32.html#associatedconstant.BITS)

These APIs are now stable in const contexts:

- [`char::from_u32`]
  (https://doc.rust-lang.org/stable/std/primitive.char.html#method.from_u32)
- [`char::from_digit`]
  (https://doc.rust-lang.org/stable/std/primitive.char.html#method.from_digit)
- [`char::to_digit`]
  (https://doc.rust-lang.org/stable/std/primitive.char.html#method.to_digit)
- [`core::char::from_u32`]
  (https://doc.rust-lang.org/stable/core/char/fn.from_u32.html)
- [`core::char::from_digit`]
  (https://doc.rust-lang.org/stable/core/char/fn.from_digit.html)

Compatibility Notes
-------------------

- [The layout of `repr(Rust)` types now groups m\*2^n-sized fields
  with equivalently aligned ones.]
  (rust-lang/rust#102750) This is intended
  to be an optimization, but it is also known to increase type
  sizes in a few cases for the placement of enum tags. As a reminder,
  the layout of `repr(Rust)` types is an implementation detail,
  subject to change.
- [0.5 now rounds to 0 when formatted to 0 decimal places.]
  (rust-lang/rust#102935)
  This makes it consistent with the rest of floating point formatting that
  rounds ties toward even digits.
- [Chains of `&&` and `||` will now drop temporaries from their
  sub-expressions in evaluation order, left-to-right.]
  (rust-lang/rust#103293) Previously, it
  was "twisted" such that the _first_ expression dropped its
  temporaries _last_, after all of the other expressions dropped
  in order.
- [Underscore suffixes on string literals are now a hard error.]
  (rust-lang/rust#103914)
  This has been a future-compatibility warning since 1.20.0.
- [Stop passing `-export-dynamic` to `wasm-ld`.]
  (rust-lang/rust#105405)
- [`main` is now mangled as `__main_void` on `wasm32-wasi`.]
  (rust-lang/rust#105468)
- [Cargo now emits an error if there are multiple registries in
  the configuration with the same index URL.]
  (rust-lang/cargo#10592)

Internal Changes
----------------

These changes do not affect any public interfaces of Rust, but they
represent significant improvements to the performance or internals
of rustc and related tools.

- [Rewrite LLVM's archive writer in Rust.]
  (rust-lang/rust#97485)

Add new MIR constant propagation based on dataflow analysis

The current constant propagation in `rustc_mir_transform/src/const_prop.rs` fails to handle many cases that would be expected from a constant propagation optimization. For example:
```rust
let x = if true { 0 } else { 0 };
```
This pull request adds a new constant propagation MIR optimization pass based on the existing dataflow analysis framework. Since most of the analysis is not unique to constant propagation, a generic framework has been extracted. It works on top of the existing framework and could be reused for other optimzations.

Closes #80038. Closes #81605.

## Todo
### Essential
- [x] [Writes to inactive enum variants](rust-lang/rust#101168 (review)). Resolved by rejecting the registration of places with downcast projections for now. Could be improved by flooding other variants if mutable access to a variant is observed.
- [X] Handle [`StatementKind::CopyNonOverlapping`](rust-lang/rust#101168 (comment)). Resolved by flooding the destination.
- [x] Handle `UnsafeCell` / `!Freeze` correctly.
- [X] Overflow propagation of `CheckedBinaryOp`: Decided to not propagate if overflow flag is `true` (`false` will still be propagated)
- [x] More documentation in general.
- [x] Arguments for correctness, documentation of necessary assumptions.
- [x] Better performance, or alternatively, require `-Zmir-opt-level=3` for now.

### Extra
- [x]  Add explicit unreachability, i.e. upgrading the lattice from $\mathbb{P} \to \mathbb{V}$ to $\set{\bot} \cup (\mathbb{P} \to \mathbb{V})$.
- [x] Use storage statements to improve precision.
- [ ] Consider opening issue for duplicate diagnostics: rust-lang/rust#101168 (comment)
- [ ] Flood moved-from places with $\bot$ (requires some changes for places with tracked projections).
- [ ] Add downcast projections back in.
- [ ] [Algebraic simplifications](rust-lang/rust#101168 (comment)) (possibly with a shared API; done by old const prop).
- [ ] Propagation through slices / arrays.
- [ ] Find other optimizations that are done by old `const_prop.rs`, but not by this one.

Add new MIR constant propagation based on dataflow analysis

The current constant propagation in `rustc_mir_transform/src/const_prop.rs` fails to handle many cases that would be expected from a constant propagation optimization. For example:
```rust
let x = if true { 0 } else { 0 };
```
This pull request adds a new constant propagation MIR optimization pass based on the existing dataflow analysis framework. Since most of the analysis is not unique to constant propagation, a generic framework has been extracted. It works on top of the existing framework and could be reused for other optimzations.

Closes #80038. Closes #81605.

## Todo
### Essential
- [x] [Writes to inactive enum variants](rust-lang/rust#101168 (review)). Resolved by rejecting the registration of places with downcast projections for now. Could be improved by flooding other variants if mutable access to a variant is observed.
- [X] Handle [`StatementKind::CopyNonOverlapping`](rust-lang/rust#101168 (comment)). Resolved by flooding the destination.
- [x] Handle `UnsafeCell` / `!Freeze` correctly.
- [X] Overflow propagation of `CheckedBinaryOp`: Decided to not propagate if overflow flag is `true` (`false` will still be propagated)
- [x] More documentation in general.
- [x] Arguments for correctness, documentation of necessary assumptions.
- [x] Better performance, or alternatively, require `-Zmir-opt-level=3` for now.

### Extra
- [x]  Add explicit unreachability, i.e. upgrading the lattice from $\mathbb{P} \to \mathbb{V}$ to $\set{\bot} \cup (\mathbb{P} \to \mathbb{V})$.
- [x] Use storage statements to improve precision.
- [ ] Consider opening issue for duplicate diagnostics: rust-lang/rust#101168 (comment)
- [ ] Flood moved-from places with $\bot$ (requires some changes for places with tracked projections).
- [ ] Add downcast projections back in.
- [ ] [Algebraic simplifications](rust-lang/rust#101168 (comment)) (possibly with a shared API; done by old const prop).
- [ ] Propagation through slices / arrays.
- [ ] Find other optimizations that are done by old `const_prop.rs`, but not by this one.

Add new MIR constant propagation based on dataflow analysis

The current constant propagation in `rustc_mir_transform/src/const_prop.rs` fails to handle many cases that would be expected from a constant propagation optimization. For example:
```rust
let x = if true { 0 } else { 0 };
```
This pull request adds a new constant propagation MIR optimization pass based on the existing dataflow analysis framework. Since most of the analysis is not unique to constant propagation, a generic framework has been extracted. It works on top of the existing framework and could be reused for other optimzations.

Closes #80038. Closes #81605.

## Todo
### Essential
- [x] [Writes to inactive enum variants](rust-lang/rust#101168 (review)). Resolved by rejecting the registration of places with downcast projections for now. Could be improved by flooding other variants if mutable access to a variant is observed.
- [X] Handle [`StatementKind::CopyNonOverlapping`](rust-lang/rust#101168 (comment)). Resolved by flooding the destination.
- [x] Handle `UnsafeCell` / `!Freeze` correctly.
- [X] Overflow propagation of `CheckedBinaryOp`: Decided to not propagate if overflow flag is `true` (`false` will still be propagated)
- [x] More documentation in general.
- [x] Arguments for correctness, documentation of necessary assumptions.
- [x] Better performance, or alternatively, require `-Zmir-opt-level=3` for now.

### Extra
- [x]  Add explicit unreachability, i.e. upgrading the lattice from $\mathbb{P} \to \mathbb{V}$ to $\set{\bot} \cup (\mathbb{P} \to \mathbb{V})$.
- [x] Use storage statements to improve precision.
- [ ] Consider opening issue for duplicate diagnostics: rust-lang/rust#101168 (comment)
- [ ] Flood moved-from places with $\bot$ (requires some changes for places with tracked projections).
- [ ] Add downcast projections back in.
- [ ] [Algebraic simplifications](rust-lang/rust#101168 (comment)) (possibly with a shared API; done by old const prop).
- [ ] Propagation through slices / arrays.
- [ ] Find other optimizations that are done by old `const_prop.rs`, but not by this one.

Add new MIR constant propagation based on dataflow analysis

The current constant propagation in `rustc_mir_transform/src/const_prop.rs` fails to handle many cases that would be expected from a constant propagation optimization. For example:
```rust
let x = if true { 0 } else { 0 };
```
This pull request adds a new constant propagation MIR optimization pass based on the existing dataflow analysis framework. Since most of the analysis is not unique to constant propagation, a generic framework has been extracted. It works on top of the existing framework and could be reused for other optimzations.

Closes #80038. Closes #81605.

## Todo
### Essential
- [x] [Writes to inactive enum variants](rust-lang/rust#101168 (review)). Resolved by rejecting the registration of places with downcast projections for now. Could be improved by flooding other variants if mutable access to a variant is observed.
- [X] Handle [`StatementKind::CopyNonOverlapping`](rust-lang/rust#101168 (comment)). Resolved by flooding the destination.
- [x] Handle `UnsafeCell` / `!Freeze` correctly.
- [X] Overflow propagation of `CheckedBinaryOp`: Decided to not propagate if overflow flag is `true` (`false` will still be propagated)
- [x] More documentation in general.
- [x] Arguments for correctness, documentation of necessary assumptions.
- [x] Better performance, or alternatively, require `-Zmir-opt-level=3` for now.

### Extra
- [x]  Add explicit unreachability, i.e. upgrading the lattice from $\mathbb{P} \to \mathbb{V}$ to $\set{\bot} \cup (\mathbb{P} \to \mathbb{V})$.
- [x] Use storage statements to improve precision.
- [ ] Consider opening issue for duplicate diagnostics: rust-lang/rust#101168 (comment)
- [ ] Flood moved-from places with $\bot$ (requires some changes for places with tracked projections).
- [ ] Add downcast projections back in.
- [ ] [Algebraic simplifications](rust-lang/rust#101168 (comment)) (possibly with a shared API; done by old const prop).
- [ ] Propagation through slices / arrays.
- [ ] Find other optimizations that are done by old `const_prop.rs`, but not by this one.