fix(handlers): disable filesystem layer link metadata if the database is enabled
Fixes: gitlab-com/gl-infra/production#14260 (closed)
During a refactor, we removed migration mode, but we also removed logic which disables writing and reading for FS metadata: v3.71.0-gitlab...v3.73.0-gitlab
This caused serving blobs to fail here, since it tried to Stat their FS metadata: https://gitlab.com/gitlab-org/container-registry/-/blob/v3.73.0-gitlab/registry/storage/linkedblobstore.go#L76
Edited by Suleimi Ahmed