Container Registry GraphqQL: add search and sorting on tag name

In a recent Slack discussion, we agreed on the value of being able to search and sort on tag names in the container registry details page.

To achieve this we need to add some more functionality to our models and expose it through the GraphQL API.

We can then build up the frontend search and sorting using the usual standard component (same as in the list page)

This is doable on the rails side, without having to wait for the registry metadata, because we are already fetching the complete list of tags from the registry.