…yUwU

Do not normalize closure signature when building `FnOnce` shim

It is not necessary to normalize the closure signature when building an `FnOnce` shim for an `Fn`/`FnMut` closure. That closure shim is just calling `FnMut::call_mut(&mut self)` anyways.

It's also somewhat sketchy that we were ever doing this to begin with, since we're normalizing with a `ParamEnv::reveal_all()` param-env, which is definitely not right with possibly polymorphic substs.

This cuts out a tiny bit of unnecessary work in `Instance::resolve` and simplifies the signature because now we can unconditionally return an `Instance`.

Rollup of 12 pull requests

Successful merges:

 - rust-lang#112806 (Small code improvements in `collect_intra_doc_links.rs`)
 - rust-lang#119460 (coverage: Never emit improperly-ordered coverage regions)
 - rust-lang#119766 (Split tait and impl trait in assoc items logic)
 - rust-lang#120062 (llvm: change data layout bug to an error and make it trigger more)
 - rust-lang#120099 (linker: Refactor library linking methods in `trait Linker`)
 - rust-lang#120139 (Do not normalize closure signature when building `FnOnce` shim)
 - rust-lang#120160 (Manually implement derived `NonZero` traits.)
 - rust-lang#120171 (Fix assume and assert in jump threading)
 - rust-lang#120183 (Add `#[coverage(off)]` to closures introduced by `#[test]` and `#[bench]`)
 - rust-lang#120195 (add several resolution test cases)
 - rust-lang#120259 (Split Diagnostics for Uncommon Codepoints: Add List to Display Characters Involved)
 - rust-lang#120261 (Provide structured suggestion to use trait objects in some cases of `if` arm type divergence)

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

Rollup of 9 pull requests

Successful merges:

 - rust-lang#112806 (Small code improvements in `collect_intra_doc_links.rs`)
 - rust-lang#119766 (Split tait and impl trait in assoc items logic)
 - rust-lang#120139 (Do not normalize closure signature when building `FnOnce` shim)
 - rust-lang#120160 (Manually implement derived `NonZero` traits.)
 - rust-lang#120171 (Fix assume and assert in jump threading)
 - rust-lang#120183 (Add `#[coverage(off)]` to closures introduced by `#[test]` and `#[bench]`)
 - rust-lang#120195 (add several resolution test cases)
 - rust-lang#120259 (Split Diagnostics for Uncommon Codepoints: Add List to Display Characters Involved)
 - rust-lang#120261 (Provide structured suggestion to use trait objects in some cases of `if` arm type divergence)

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

Rollup merge of rust-lang#120139 - compiler-errors:fnonce-shim, r=BoxyUwU

Do not normalize closure signature when building `FnOnce` shim

It is not necessary to normalize the closure signature when building an `FnOnce` shim for an `Fn`/`FnMut` closure. That closure shim is just calling `FnMut::call_mut(&mut self)` anyways.

It's also somewhat sketchy that we were ever doing this to begin with, since we're normalizing with a `ParamEnv::reveal_all()` param-env, which is definitely not right with possibly polymorphic substs.

This cuts out a tiny bit of unnecessary work in `Instance::resolve` and simplifies the signature because now we can unconditionally return an `Instance`.