Resolve "API endpoint to list the Docker images/tags of a group"

What does this MR do?

API endpoints for requesting docker container repository information using only the Group rather than Project have been added. Users can view all container repositories within a group, as well as all of those container repositories with tag details. The project id does not need to be known to make these requests.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance and testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Related to #26866 (closed)