Metrics and dashboards improvements
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 (gitlab-org&5523 (closed)). This will be achieved following the gradual migration plan detailed in gitlab-org/container-registry#374 (closed).
Task
Go through the list of Prometheus metrics and Grafana dashboards for the registry and ensure that everything is working as expected and displayed accurately. This is a good opportunity not only for fixes but also for generic improvements.
Edited by João Pereira