[llvm] [VPlan] Replace VPRecipeOrVPValue with VP2VP recipe simplification. (PR #76090)

[via llvm-commits]

https://github.com/ayalz commented:

Nice cleanup, thanks for pursuing!

Wonder if `tryTo*()`'s should return more specific recipes than `VPRecipeBase*`, as in `tryToBlend()`.

https://github.com/llvm/llvm-project/pull/76090