[llvm] [AMDGPU] Fold away S_AND of a lane mask with EXEC (PR #227729)

[Jay Foad via llvm-commits]

jayfoad wrote:

> It's fairly simple to remove the optimization from optimizeVccBranch after this, but it involves updating a few tests, so I'll do it as a separate PR.

#228417.

https://github.com/llvm/llvm-project/pull/227729