[llvm] [VPlan] Iterate over header phis to determine FORs that need EVL fixup. NFCI (PR #147032)

[Mel Chen via llvm-commits]

https://github.com/Mel-Chen approved this pull request.

LGTM, but `transformRecipestoEVLRecipes` is getting large — would it make sense to extract this part into a static helper function for better readability?

https://github.com/llvm/llvm-project/pull/147032