Add pagination and new routing for docker container registry

What does this MR do?

This MR adds pagination to the ContainerRepositoriesSerializer and also adds show actions for the group and project RepositoriesControllers. The show action invokes the index action (so both have identical responses). The response is the same because the front end of the index and show pages for these views are a single Vue app, so if a user visits either the index or a show url, we want the same json payload to be returned to the front end to enable it's SPA abilities.

⚠ !23079 (closed) this is the POC that generated this MR ⚠

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability 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

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 #23315 (closed)