Rollup of 16 pull requests

Successful merges:

 - rust-lang#79023 (Add `core::stream::Stream`)
 - rust-lang#80562 (Consider Scalar to be a bool only if its unsigned)
 - rust-lang#80886 (Stabilize raw ref macros)
 - rust-lang#80959 (Stabilize `unsigned_abs`)
 - rust-lang#81291 (Support FRU pattern with `[feature(capture_disjoint_fields)]`)
 - rust-lang#81409 (Slight simplification of chars().count())
 - rust-lang#81468 (cfg(version): treat nightlies as complete)
 - rust-lang#81473 (Warn write-only fields)
 - rust-lang#81495 (rustdoc: Remove unnecessary optional)
 - rust-lang#81499 (Updated Vec::splice documentation)
 - rust-lang#81501 (update rustfmt to v1.4.34)
 - rust-lang#81505 (`fn cold_path` doesn't need to be pub)
 - rust-lang#81512 (Add missing variants in match binding)
 - rust-lang#81515 (Fix typo in pat.rs)
 - rust-lang#81519 (Don't print error output from rustup when detecting default build triple)
 - rust-lang#81520 (Don't clone LLVM submodule when download-ci-llvm is set)

Failed merges:

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

Make #[cfg(version)] respect RUSTC_OVERRIDE_VERSION_STRING

The `#[cfg(version(...))]` feature is currently under-tested. Part of it is the difficulty that it is hard to write a test that never changes, while the version of the Rust compiler indeed *does* change.

PR rust-lang#81468 added the first and so far only test of `#[cfg(version(...))]`'s functionality (there is one other test for the *syntax*, that also acts as feature gate). But that test uses a proc macro that parses the version: the text of the test doesn't contain the actual `#[cfg(version(...))]`.

This PR makes `#[cfg(version(...))]` respect `RUSTC_OVERRIDE_VERSION_STRING`, added by PR rust-lang#124339, allowing us to virtually pin the rustc version and write tests from all directions against some specific version.

The PR also adds a functional test of `#[cfg(version(...))]` that leverages `RUSTC_OVERRIDE_VERSION_STRING`.

Pulled out of rust-lang#141137.

Tracking issue: rust-lang#64796

Make #[cfg(version)] respect RUSTC_OVERRIDE_VERSION_STRING

The `#[cfg(version(...))]` feature is currently under-tested. Part of it is the difficulty that it is hard to write a test that never changes, while the version of the Rust compiler indeed *does* change.

PR rust-lang#81468 added the first and so far only test of `#[cfg(version(...))]`'s functionality (there is one other test for the *syntax*, that also acts as feature gate). But that test uses a proc macro that parses the version: the text of the test doesn't contain the actual `#[cfg(version(...))]`.

This PR makes `#[cfg(version(...))]` respect `RUSTC_OVERRIDE_VERSION_STRING`, added by PR rust-lang#124339, allowing us to virtually pin the rustc version and write tests from all directions against some specific version.

The PR also adds a functional test of `#[cfg(version(...))]` that leverages `RUSTC_OVERRIDE_VERSION_STRING`.

Pulled out of rust-lang#141137.

Tracking issue: rust-lang#64796

Make #[cfg(version)] respect RUSTC_OVERRIDE_VERSION_STRING

The `#[cfg(version(...))]` feature is currently under-tested. Part of it is the difficulty that it is hard to write a test that never changes, while the version of the Rust compiler indeed *does* change.

PR rust-lang#81468 added the first and so far only test of `#[cfg(version(...))]`'s functionality (there is one other test for the *syntax*, that also acts as feature gate). But that test uses a proc macro that parses the version: the text of the test doesn't contain the actual `#[cfg(version(...))]`.

This PR makes `#[cfg(version(...))]` respect `RUSTC_OVERRIDE_VERSION_STRING`, added by PR rust-lang#124339, allowing us to virtually pin the rustc version and write tests from all directions against some specific version.

The PR also adds a functional test of `#[cfg(version(...))]` that leverages `RUSTC_OVERRIDE_VERSION_STRING`.

Pulled out of rust-lang#141137.

Tracking issue: rust-lang#64796

Rollup merge of #141413 - est31:cfg_version_env_var, r=jieyouxu

Make #[cfg(version)] respect RUSTC_OVERRIDE_VERSION_STRING

The `#[cfg(version(...))]` feature is currently under-tested. Part of it is the difficulty that it is hard to write a test that never changes, while the version of the Rust compiler indeed *does* change.

PR #81468 added the first and so far only test of `#[cfg(version(...))]`'s functionality (there is one other test for the *syntax*, that also acts as feature gate). But that test uses a proc macro that parses the version: the text of the test doesn't contain the actual `#[cfg(version(...))]`.

This PR makes `#[cfg(version(...))]` respect `RUSTC_OVERRIDE_VERSION_STRING`, added by PR #124339, allowing us to virtually pin the rustc version and write tests from all directions against some specific version.

The PR also adds a functional test of `#[cfg(version(...))]` that leverages `RUSTC_OVERRIDE_VERSION_STRING`.

Pulled out of #141137.

Tracking issue: #64796