Deploy and migrate the new container registry for GitLab.com (Phase 2)
## Context
This is part of the work to upgrade and migrate the GitLab.com container registry to a new version backed by a metadata database and online garbage collection (https://gitlab.com/groups/gitlab-org/-/epics/5523). This will be achieved following the gradual migration plan detailed in https://gitlab.com/gitlab-org/container-registry/-/issues/374.
This specific epic is meant to collect the tasks required for [Phase 2](https://gitlab.com/gitlab-org/container-registry/-/issues/374#phase-2-migrate-existing-repositories) of the migration plan.
## Status
In progress. See https://gitlab.com/groups/gitlab-org/-/epics/5523#updates for updates.
epic