[NFC][Coroutines] Remove integer indexing in several CoroSplit loops#115954

TylerNowicki merged 2 commits intollvm:mainllvm/llvm-project:mainfrom

TylerNowicki:amd/dev/tnowicki/replace.int.loop.countersTylerNowicki/llvm-project:amd/dev/tnowicki/replace.int.loop.countersCopy head branch name to clipboard