Add tags_count to container registry api and controller

Merged Nicolò Maria Mezzopera requested to merge 216757-add-tags-count into master

What does this MR do?

This MR adds tags_count to the container registry APIs and controllers.

In the API returning the count is configurable with a parameter, in the controller since the UI will need it all the time the value is always returned.

This MR was co-authored by:

Screenshots

No visual changes

Does this MR meet the acceptance criteria?

Conformity

Availability and Testing

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

  • [-] Label as security and @ mention @gitlab-com/gl-security/appsec
  • [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
  • [-] Security reports checked/validated by a reviewer from the AppSec team

Part of #216757 (closed)

Edited by Nicolò Maria Mezzopera