Refactor out the parallel move algorithm into a helper class, and add
stack slot support for cases where stack slots can clobber each other
(e.g. a Phi which is an input to another Phi). Also add some
documentation for how these parallel moves work.

Bug: v8:7700
Change-Id: Ib9bb1cce8287e2ad34b4417b77b148a1ad483268
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3803032Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82113}