MIR move elimination [4/6]: MoveElimination

[Amanieu]

Depends on #163336 and #163337

This PR implements the MoveElimination pass from rust-lang/rfcs#3943.

This pass uses the analysis results from PreciseLiveness to unify locals that are related by an assignment. This also includes an alias-fixup pass which is needed because some rvalues don't allow sources to overlap with the destination place.

The pass is only enabled under -Zmir-move-elimination. This flag also disables DestinationPropagation, which is superseded by the new pass.

r? tmiasko

[Amanieu]

LLM disclosure: LLMs were used to generate the boilerplate for the MIR tests, but each test was manually reviewed and adjusted before committing. LLMs were also used to audit this pass against the rest of the compiler MIR transforms and Miri semantics.

[rustbot]

This PR changes MIR

cc @oli-obk, @RalfJung, @JakobDegen, @vakaras

Some changes occurred in compiler/rustc_attr_parsing

cc @jdonszelmann, @JonathanBrouwer

Some changes occurred in compiler/rustc_attr_ir

cc @jdonszelmann, @JonathanBrouwer

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

This PR changes rustc_public

cc @oli-obk, @celinval, @ouz-a, @makai410

[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.

[Amanieu]

Rebased on top of main which now contains #163337. This PR now only has the commits related to the main MoveElimination pass.