[llvm] [StackColoring] Delete dead stack slots (PR #72633)

[Piotr Sobczak via llvm-commits]

piotrAMD wrote:

The change is causing the assertion for me in "ninja check-llvm" on linux:
llc: /upstream/llvm/include/llvm/CodeGen/MachineFrameInfo.h:530: int64_t llvm::MachineFrameInfo::getObjectOffset(int) const: Assertion `!isDeadObjectIndex(ObjectIdx) && "Getting frame offset for a dead object?"' failed.

https://github.com/llvm/llvm-project/pull/72633