Replace calls to old repo-updater store and types by the new store

Created by: asdine

This PR removes the repo-updater Store type and replaces all calls to that store by the new one. Services outside of repo-updater now use the internal/db stores instead of relying on repo-updater. All repo-updater Repo and ExternalService types have been removed, and their logic transfered to types.Repo and types.ExternalService.

Fixes #14710 (closed) #14711 (closed) #14712 (closed)