[llvm] [VPlan] Add vputils::recipesOnly that returns a downcasted range (NFC) (PR #222770)

[Luke Lau via llvm-commits]

https://github.com/lukel97 commented:

I don't think anything about this is specific to VPRecipe. Have you considered putting it in STLExtras.h?

https://github.com/llvm/llvm-project/pull/222770