[llvm] [AMDGPU] Added hot-block-rematerialize pass (PR #136631)

[Shilei Tian via llvm-commits]

https://github.com/shiltian commented:

Just a quick drive-by with some surface-level style comments. Can you go through your entire PR and make sure everything conforms to LLVM coding style?

https://github.com/llvm/llvm-project/pull/136631