[llvm] [X86] Compress masked VPBLENDM using VBLENDV (PR #221838)

[Oscar Priego via llvm-commits]

Opriego wrote:

> please merge against trunk latest

The prerequisite change has landed, so I rebased this PR onto the latest `main` and removed the previous dependency. It now contains only the change for #221678.

I also updated the existing CodeGen checks affected by the new fold, and the PR is ready for review now. Thanks!


https://github.com/llvm/llvm-project/pull/221838