[llvm] [LV, VP]VP intrinsics support for the Loop Vectorizer + adding new tail-folding mode using EVL. (PR #76172)

[via llvm-commits]

appujee wrote:

@alexey-bataev @fhahn 

As Ayal has not responded to the patch in weeks (https://github.com/llvm/llvm-project/pull/76172#issuecomment-1942735278) even after pinging, should we follow up in a post commit review if and when Ayal has feedback?

https://github.com/llvm/llvm-project/pull/76172