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

[Jay Foad via llvm-commits]

jayfoad wrote:

Here's one for `-amdgpu-remat-enable-hot-block-remat-aggressive` which fails an assertion "Invalid RC for virtual register": [r2.txt](https://github.com/user-attachments/files/19468032/r2.txt)


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