repo-updater: Stream GitHub last configs in lists first
Created by: keegancsmith
This commit is making the observation that admins usually add repos/configurations to the end of lists. We now eagerly insert new repositories. So by processing GitHub configurations such that we first stream the end of the repos list, will likely lead to the new repository appearing sooner. The same assumption is applied to repository queries and orgs.
Part of https://github.com/sourcegraph/sourcegraph/issues/5145