feat[nutmeg]: add new endpoint for cloning course [BB-7106]

[pkulkark]

This backports openedx#31794 to Nutmeg.

Adds a new studio endpoint for the existing clone_course method, so that external applications can call it using the following API:

/api/v1/course_runs/clone/

And passing the source_course_id (of an existing course) and destination_course_id (of a non-existing course) in the request data, like below:

{
    "source_course_id": "course-v1:edX+DemoX+Demo_Course",
    "destination_course_id": "course-v1:new+TestX+Demo_Course_Clone",
}

See parent PR for testing instructions.

[Cup0fCoffee]

👍

• I tested this: I tested it while reviewing [BB-7106] Add new endpoint for cloning course openedx/openedx-platform#31794
• I read through the code
• [N/A] I checked for accessibility issues