[VPlan] Remove PtrIV::IsScalarAfterVectorization, use VPlan analysis.#168289

fhahn wants to merge 2 commits intollvm:mainllvm/llvm-project:mainfrom

fhahn:vplan-check-scalar-user-ptr-ivfhahn/llvm-project:vplan-check-scalar-user-ptr-ivCopy head branch name to clipboard