[llvm] [X86] Fold chained i32 CLMUL operands (PR #202250)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon requested changes to this pull request.

ensure new tests are added as the first commit in the PR with base codegen, and then the codegen changes in follow up commits - we squash when the PR is accepted but it helps with review

https://github.com/llvm/llvm-project/pull/202250