[llvm] [VPlan] Introduce VPlanConstantFolder (PR #125365)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

Thanks for the review: I've now moved the logic to simplifyRecipe, leaving a couple of TODOs. If this is the desired approach, we can improve upon it in follow-ups.

https://github.com/llvm/llvm-project/pull/125365