[llvm] [AArch64][LoopIdiom] Generalize AArch64LoopIdiomTransform into LoopIdiomVectorize (PR #94081)

[Min-Yih Hsu via llvm-commits]

mshockwave wrote:

I have now reverted all the intrusive refactoring. I'm planning to create two additional PRs:
  1. Factoring out the part that differs between masked v.s. VP vectorization. Will be NFC.
  2. I found that some of the DominatorTreeUpdates are redundant. I will put such simplifications in a separate PR. But it's still effectively a NFC.

https://github.com/llvm/llvm-project/pull/94081