move artifacts storage to MinIO

In #41402 (closed), @lavamind noticed that all (confirmed?) of the /srv/gitlab-shared is used by artifacts. In parallel, we've started moving more and more storage to MinIO as an object storage backend.

We should consider moving artifacts to MinIO as well. It would make the main GitLab server more nimble as it would reduce storage to a handful of things remaining, I believe the PostgreSQL database and Gitaly.

It could possibly reduce the load on the server as artifacts could be pushed to MinIO from runners directly and served from there directly as well (to be confirmed!).

One critical aspect of this is that MinIO currently does not have proper backups. This would need to be fixed, either in-band by making sure MinIO is backed up properly or out-of-band, by ensuring GitLab extracts artifacts and backs them up to the storage server somehow.