feat: add CRUD support for RestrictedCourseRun in CourseRun Api

[zawan-ila]

PROD-4004

This PR adds support for marking CourseRuns as restricted through the CourseRun Api

Testing Instructions:

You can test it by hitting the API directly with postman or any other tool and provide the restriction_type parameter. Then verify that the RestrictedCourseRun objects are added/updated appropriately in the database.

Here's how I have been doing it though.

• Apply the attached patch to Publisher restriction.patch
• Create/Update runs as you would normally.
• However, just before clicking the Create/Update button, set window.restriction_type to whatever restriction_type you want to set.
• Observe that the objects are created/updated properly in the backend.

[DawoudSheraz]

Overall, the PR looks good. I have not had a chance to test it out on the local yet.