[llvm] [AMDGPU][Scheduler] Refactor ArchVGPR rematerialization during scheduling (PR #125885)

[Jeffrey Byrnes via llvm-commits]

https://github.com/jrbyrnes approved this pull request.

This LGTM, but it would be good to wait for someone else to take a look due to the amount of change.

https://github.com/llvm/llvm-project/pull/125885