[ConstantFold] Support scalable constant splats in ConstantFoldCastInstruction#133207

lukel97 merged 6 commits intollvm:mainllvm/llvm-project:mainfrom

lukel97:instcombine/constant-fold-scalable-splat-castlukel97/llvm-project:instcombine/constant-fold-scalable-splat-castCopy head branch name to clipboard