[llvm] [ConstraintElim] Decompose sext-like insts for signed predicates (PR #82344)

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

Thanks, would be good to have tests independent of min/max as well. Could you submit the tests separately?

https://github.com/llvm/llvm-project/pull/82344