Add a Container Registry test for Self-managed instances

Description of the test

Adds a Container Registry for self-managed GitLab instances.

The configuration for this test varies on the gitlab-ci.yml as the GitLab managed environments do not require explicit instructions for TLS with docker executors

It does not remove the repository at the end of the test as the instance is destroyed as well.

Uses the ssh_tunnel scenario that gives a hostname exposing it to the internet.

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