Create cluster management project automatically

What does this MR do?

This is the first step towards using a cluster management project for all GitLab-managed cluster applications. It adds the (currently unused) logic that will be used to create a cluster management project automatically.

Key points:

• Project creation is controlled by the :auto_create_cluster_management_project feature flag, which defaults to false.
• The created project is currently empty, and would require input from the user to enable managing applications with it. The next iteration will populate the project from a template.
• The cluster management project is private, with maintainer users added as follows:
  • project cluster: maintainers of the project (group and instance clusters will inherit members automatically)

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

#37964 (closed)