Test container registry in staging

Description of the test

This is a test to be specifically run against staging.

This is to prioritize the testing of the new metadata database and garbage collection which will come first to gitlab.com and later to self-manage customers (omnibus).

This is the simplest iteration of the registry where we can build and push a docker image from a project to the registry, verify it is created, and delete the image.

Check-list

• Confirm the test has a testcase: tag linking to an existing test case in the test case project.
• Note if the test is intended to run in specific scenarios. If a scenario is new, add a link to the MR that adds the new scenario.
• Follow the end-to-end tests style guide and best practices.
• Use the appropriate RSpec metadata tag(s).
• Ensure that a created resource is removed after test execution.
• Ensure that no transient bugs are hidden accidentally due to the usage of waits and reloads.
• Verify the tags to ensure it runs on the desired test environments.
• If this MR has a dependency on another MR, such as a GitLab QA MR, specify the order in which the MRs should be merged.
• (If applicable) Create a follow-up issue to document the special setup necessary to run the test: ISSUE_LINK