Assign custom Compliance Framework Labels to projects

What does this MR do?

• Adds ability to assign custom compliance labels to projects.
• Behind a default-off feature flag.
• Adds documentation that assumes the ability to create new labels via the web UI is not yet available so it can be merged without dependency on #287827 (closed). (cc @rob.hunt)
• Changes permissions required to change a projects compliance framework to above project maintainer. 💥 Breaking change 💥
  • Moving this to a separate issue. ☝

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry Behind default-off feature flag
• 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
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

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

Related to #276221 (closed)