Remove #![feature(let_chains)] from library and src/librustdoc

PR rust-lang#132833 has stabilized the `let_chains` feature. This PR removes the last occurences from the library, the compiler, and librustdoc (also because rust-lang#140887 missed the conditional in one of the crates as it was behind the "rustc" feature).

Remove #![feature(let_chains)] from library and src/librustdoc

PR rust-lang#132833 has stabilized the `let_chains` feature. This PR removes the last occurences from the library, the compiler, and librustdoc (also because rust-lang#140887 missed the conditional in one of the crates as it was behind the "rustc" feature).

…mpiler-errors

Rollup of 14 pull requests

Successful merges:

 - rust-lang#139749 (docs(library/core/src/pin): fix typo "necessarily" -> "necessary")
 - rust-lang#140130 (Add LLDB providers for BTreeMap and BTreeSet)
 - rust-lang#140685 (Simplify `Vec::as_non_null` implementation and make it `const`)
 - rust-lang#140712 (normalization: avoid incompletely constraining GAT args)
 - rust-lang#140768 (Improve `dangerous_implicit_aurorefs` diagnostic output)
 - rust-lang#140834 (move (or remove) some impl Trait tests)
 - rust-lang#140910 (Remove `stable` attribute from wasi fs (read_exact|write_all)_at)
 - rust-lang#140947 (Flush errors before deep normalize in `dropck_outlives`)
 - rust-lang#140966 (Remove #![feature(let_chains)] from library and src/librustdoc)
 - rust-lang#140977 ([win] Use a dash instead of slash for linker to avoid breaking lld)
 - rust-lang#140990 (VxWorks: updates from recent libc versions)
 - rust-lang#141003 (Improve ternary operator recovery)
 - rust-lang#141013 (Implement methods to set STARTUPINFO flags for Command API on Windows)
 - rust-lang#141026 (rustc-dev-guide subtree update)

r? `@ghost`
`@rustbot` modify labels: rollup

…iaskrgr

Rollup of 8 pull requests

Successful merges:

 - rust-lang#139749 (docs(library/core/src/pin): fix typo "necessarily" -> "necessary")
 - rust-lang#140685 (Simplify `Vec::as_non_null` implementation and make it `const`)
 - rust-lang#140712 (normalization: avoid incompletely constraining GAT args)
 - rust-lang#140768 (Improve `dangerous_implicit_aurorefs` diagnostic output)
 - rust-lang#140947 (Flush errors before deep normalize in `dropck_outlives`)
 - rust-lang#140966 (Remove #![feature(let_chains)] from library and src/librustdoc)
 - rust-lang#140990 (VxWorks: updates from recent libc versions)
 - rust-lang#141027 (remove `RustfmtState` to reduce `initial_rustfmt` complexity)

r? `@ghost`
`@rustbot` modify labels: rollup

Remove #![feature(let_chains)] from library and src/librustdoc

PR rust-lang#132833 has stabilized the `let_chains` feature. This PR removes the last occurences from the library, the compiler, and librustdoc (also because rust-lang#140887 missed the conditional in one of the crates as it was behind the "rustc" feature).

We keep `core` as exercise for the future as updating it is non-trivial (see PR thread).

Rollup of 6 pull requests

Successful merges:

 - rust-lang#127013 (Add `f16` formatting and parsing)
 - rust-lang#140154 (Cygwin support in rustc)
 - rust-lang#140628 (std: stop using TLS in signal handler)
 - rust-lang#140966 (Remove #![feature(let_chains)] from library and src/librustdoc)
 - rust-lang#140994 (replace `cc_detect::cc2ar` with `cc::try_get_archiver`)
 - rust-lang#141127 (bump windows crate for compiler,bootstrap and tools)

r? `@ghost`
`@rustbot` modify labels: rollup

Rollup of 8 pull requests

Successful merges:

 - rust-lang#140113 (Add per page TOC in the `rustc` book)
 - rust-lang#140511 (Stabilize `#![feature(non_null_from_ref)]`)
 - rust-lang#140924 (Make some `f32`/`f64` tests also run in const-context)
 - rust-lang#140966 (Remove #![feature(let_chains)] from library and src/librustdoc)
 - rust-lang#141045 ([win][arm64] Remove 'Arm64 Hazard' undocumented MSVC option and instead disable problematic test)
 - rust-lang#141071 (Enable [behind-upstream] triagebot option for rust-lang/rust)
 - rust-lang#141132 (Use `crate::` prefix for root macro suggestions)
 - rust-lang#141139 (Fix Rust for Linux ping group label)

r? `@ghost`
`@rustbot` modify labels: rollup

Rollup merge of rust-lang#140966 - est31:let_chains_library, r=tgross35

Remove #![feature(let_chains)] from library and src/librustdoc

PR rust-lang#132833 has stabilized the `let_chains` feature. This PR removes the last occurences from the library, the compiler, and librustdoc (also because rust-lang#140887 missed the conditional in one of the crates as it was behind the "rustc" feature).

We keep `core` as exercise for the future as updating it is non-trivial (see PR thread).

Remove #![feature(let_chains)] from library and src/librustdoc

PR rust-lang#132833 has stabilized the `let_chains` feature. This PR removes the last occurences from the library, the compiler, and librustdoc (also because rust-lang#140887 missed the conditional in one of the crates as it was behind the "rustc" feature).

We keep `core` as exercise for the future as updating it is non-trivial (see PR thread).

Remove #![feature(let_chains)] from libcore

PR #132833 has stabilized the let_chains feature. This PR removes the last occurrence from the library.

Split out of #140966 as it caused breakage. Now we have a patch to the linux tree that fixes the build, so we update the linux tree to it.

cc Rust-for-Linux/linux#1163
cc #140722