[llvm] [LoopVectorizer] Prune VFs based on plan register pressure (PR #132190)

[Sam Tebbs via llvm-commits]

SamTebbs33 wrote:

Merging https://github.com/llvm/llvm-project/pull/137746 was enough to fix the mve-reduction-types.ll regression so I believe this PR is ready to land. I'll do so in a couple of days.

https://github.com/llvm/llvm-project/pull/132190