[llvm] [AMDGPU] Added hot-block-rematerialize pass (PR #126331)

[Carl Ritson via llvm-commits]

perlfu wrote:

Since this is only a draft and MirDivergence parts are going away I only I had a quick look.
I wonder if parts like AMDGPULatencyTracker should be full analysis passes, rather than just utilities?

https://github.com/llvm/llvm-project/pull/126331