Within libraries, open editors in a modal, not a new URL

[bradenmacdonald]

As an author, when I close out of an editor modal I expect to be right back where I just was, not taken to the library homepage.

As an author, I want to see at least a little bit of context when I'm editing a component. Example:

(Note how the course, section, and subsection are visible)

[kdmccormick]

Addresses an item in: openedx/edx-platform#35256 , openedx/edx-platform#35257 , and openedx/edx-platform#34692

[bradenmacdonald]

@kdmccormick I'll see what I can do when I work on this, but because we're still using the legacy Unit page, it's likely that this change is only going to be an improvement for people using these editors from a content library, and not yet from a course.

[kdmccormick]

I think that's reasonable. Plus, it gives people a reason to look forward to the new course unit editor.