[llvm] [ConstraintElimination] Add support for UCMP/SCMP intrinsics (PR #97974)

[via llvm-commits]

Poseydon42 wrote:

Rebased to use the now-merged #98177. I've left the equality check for now since I'm unsure whether the fixes suggested by @antoniofrighetto and me are viable. If they are then I'll file a separate PR with them and use the simpler equality check suggested by @dtcxzyw instead. 

https://github.com/llvm/llvm-project/pull/97974