add repo rev to predicate evaluation

Created by: camdencheek

Previously, if a predicate evaluated to a match with a specific repo rev, the rev would not be added to the expanded query. In practice, I don't think this could ever be hit because, if a repo rev was specified, the rev filter would apply after the predicate was evaluated as well, returning only results that matched the predicate-evaluated repo and the original revision-narrowed repo.

That said, there may be cases in the future where predicates can evaluate to specific revisions of a repo, and fixing this now will save some headaches down the road.

RE: https://github.com/sourcegraph/sourcegraph/pull/22666#discussion_r666037596