[llvm] [CodeGen] Extract copy-paste on PHI MachineInstr income removal. (PR #158634)

[Afanasyev Ivan via llvm-commits]

ivafanas wrote:

Inspired by comment: https://github.com/llvm/llvm-project/pull/158265#discussion_r2343831902

I suggest, if llvm already has `MachineLoopUtils.h`, it also might have `MachineInstrUtils.h` :)

https://github.com/llvm/llvm-project/pull/158634