[RISCV] Move performCombineVMergeAndVOps to RISCVVectorPeephole#144076

lukel97 merged 7 commits intollvm:mainllvm/llvm-project:mainfrom

lukel97:vector-peephole/fold-vmerge-to-masklukel97/llvm-project:vector-peephole/fold-vmerge-to-maskCopy head branch name to clipboard