[llvm] [VPlan] Perform optimizeMaskToEVL in terms of pattern matching (PR #155394)

[Ramkumar Ramachandra via llvm-commits]

https://github.com/artagnon commented:

Looks good, and the regressions are very minor. I will wait for others to comment on the big-picture.

https://github.com/llvm/llvm-project/pull/155394