License Compliance Approvals in Merge Request MVC - Add 'License-Check' approval rule to backend code to enforce policy.

Sub issue for https://gitlab.com/gitlab-org/gitlab-ee/issues/13067

Implementation Plan:

• review https://www.youtube.com/watch?v=1jaHPqszMUo
• create a project rule when License-Check is specified.
• synchronize License-Check project rule into merge request rules.
• Validate License-Check rule/policy hasn't been violated by changes in merge request.