Geo: Ensure both the repo and wiki gets synced if an `RepositoryUpdatedEvent` is processed before the project is backfilled, or if `RepositoryUpdatedEvent` is processed before `RepositoryCreatedEvent`

From https://gitlab.com/gitlab-org/gitlab-ee/issues/5876#note_108227262:

• Update (repo)-Create (repo & wiki): Repo sync race already mitigated by https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/6161, but we need to set resync_wiki to true if the registry is new_record? and there is a wiki, during ProjectRegistry#repository_updated! to ensure the wiki gets backfilled
• Update (wiki)-Create (repo & wiki): Unresolved race. We need to set resync_repository to true if the registry is new_record? during ProjectRegistry#repository_updated! to ensure the repo gets backfilled