phabricator: Simplify repo create
Created by: ryanslade
We no longer need to perform a remote call from repo-updater in order to create a Phabricator repo, we can simply call the DB directly. This removes the need for an internal handler in frontend to talk to the DB as well as the client code to call this handler.
Part of https://github.com/sourcegraph/sourcegraph/issues/36290
Test plan
All tests still pass