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

[Min-Yih Hsu via llvm-commits]

mshockwave wrote:

I'll wait for another day or so to see if there are any other comments, as I saw a reviewer from ARM has being tagged.

> 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.

This is now in #94682 

> 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.

This is now in #94681 

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