[DirectX] Simplify DXIL data scalarization, and data scalarize whole GEP chains#168096

Icohedron merged 3 commits intollvm:mainllvm/llvm-project:mainfrom

Icohedron:data-scalarization-gep-cleanupIcohedron/llvm-project:data-scalarization-gep-cleanupCopy head branch name to clipboard