Support installing and upgrading GitLab Registry

Summary

Install GitLab Registry for a GitLab instance without using GitLab Chart. Version v2alpha1 of GitLab custom resource must support the minimal specification for its configuration and description of its dependencies.

Success criteria

• GitLab Registry can be configured with a GitLab custom resource (version v2alpha1).
• GitLab Registry is installed from the specification without using GitLab Chart.
• Docker images can be pushed and pulled to the registry from the specified external URL.