The regex source generator and compiler have grown to emit more and more IndexOf variations and to do so in more and more places. Each time we add a new variation, we're having to find and augment multiple locations in the generator, and each time we identify a new vectorization opportunity, we have to be able to emit use of all of those variations. We need to consolidate most if not all of these into a single helper that can be used from multiple locations to emit the right IndexOf calls. Then when we add additional IndexOf-like support, we can do so in a single place and have it accrue value to all uses where the calls are emitted.