[llvm] [X86] Generate `kmov` for masking integers (PR #120593)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon commented:

Tests need some cleanup/simplification - ideally its good to precommit the tests with current codegen and then show the codegen change when the combine is added in a later commit.

What was the reason behind performing this in DAGToDAG and not as a regular DAG combine?

https://github.com/llvm/llvm-project/pull/120593