Add `repo:dependents` predicate to allow reverse-dependency search
Created by: mrnugget
This PR adds repo:dependents
and repo:revdeps
as search predicates, mirroring exactly what repo:dependencies
and repo:deps
do, except that the new code calls into the dependencies.(*Service).Dependents
method.
This fixes https://github.com/sourcegraph/sourcegraph/issues/32661.
Screenshot
Test plan
- Existing tests & CI