atomic volatile: add intrinsics

[RalfJung]

Extend the atomic load/store intrinsics to also support volatile atomic load/store.
Tracking issue: #158947.
Library APIs that use these intrinsics will be added inn a future PR.

The GCC and cranelift implementations ignore the volatile flag, not sure how that should be implemented for them.

[rustbot]

rustc_codegen_gcc is developed in its own repository. If possible, consider making this change to rust-lang/rustc_codegen_gcc instead.

cc @antoyo, @GuillaumeGomez

Some changes occurred to the intrinsics. Make sure the CTFE / Miri interpreter
gets adapted for the changes, if necessary.

cc @rust-lang/miri, @oli-obk, @lcnr

rustc_codegen_cranelift is developed in its own repository. If possible, consider making this change to rust-lang/rustc_codegen_cranelift instead.

cc @bjorn3

miri is developed in its own repository. If the Miri part of this change can be broken out, consider making this change to rust-lang/miri instead. However, if Miri needs adjusting for rustc changes, just ignore this message.

cc @rust-lang/miri

[rustbot]

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[nia-e]

library stuff looks fine, but the rest is not my prerogative :D

r? compiler

[bjorn3]

Cranelift doesn't currently have a way to do volatile memory operations. In the past this was not an issue given the lack of optimizations on memory operations, but those recently got added, so volatile support now needs to be added on the Cranelift side.

[rustbot]

Some changes occurred to the CTFE / Miri interpreter

cc @rust-lang/miri

Some changes occurred to the CTFE machinery

cc @oli-obk, @lcnr

[rustbot]

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.