Copy static assets when using a library component in a course (via Problem Bank or Library Content)

[bradenmacdonald]

As an author, when I use the "Problem Bank" or "Library Content" components to copy+link a component from a v2 library into my course, I expect that any static assets required for those components will be copied into the course "Files & Uploads".

As an author, I expect every course export to be complete, so that if I export a course using linked library content, and import it into another Open edX instance (even one without the associated library), the content and static assets will all be working.

Backport to Sumac as well as fixing on master. When backporting, consider including this forced rename of spaces to underscores at the same time for consistency with master.

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Note: this is already implemented for copy-paste from a library into a course, so use the same approach.