[llvm] [VPlan] Move predication to VPlanTransform (NFC). (PR #128420)

[via llvm-commits]

ayalz wrote:

> > May be worth reviewing the "native" VPlanPredicator logic introduced in https://reviews.llvm.org/D53349 and removed in https://reviews.llvm.org/D123017.
> 
> Might be good to as follow-up to potentially improve the predication implementation, once we completed the NFC move and completed the transition? Although the original l VPlanPredicator may need more work, as it was not enabled by default even in the native path and only tested via C++ unit tests.

Sure, just noting that this revives an older `VPlanPredicator.cpp` (along with its log?), which could offer some directions for improvements and/or extensions.

https://github.com/llvm/llvm-project/pull/128420