It is very annoying to have continuous builders that do not have matching tryservers; when we don't have a matching tryserver, it means that reproducing build failures is much harder.

Generally speaking we want every builder to have a matching tryserver in the commit queue. However, some configurations are too slow (or too resource intensive) to put into the CQ and still keep reasonable CQ performance. For those configs, though, we should still have matching *optional* trybots.

We do have many optional trybots, but I'm filing this bug to track getting matching optional trybots for the remaining configs and then adding some sort of presubmit check or test to make sure we enforce this.