Add a loading indicator to the Media Library.

Props kadamwhite, gcorne, kovshenin.
Fixes #24859.


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In get_site_by_path(), avoid passing $paths through prepare(). If a path contains a %, we end up with problems. see #27003.

Built from https://develop.svn.wordpress.org/trunk@27439


git-svn-id: http://core.svn.wordpress.org/trunk@27286 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Cleanup audio/video shortcodes in the media modal:

* On the controller's `update`, `replace`, and `close` events, call `detach()` on the frame
* Cleanup the HTML ouput of the Underscore templates.
* Move some logic from the Underscore template to the `VideoDetails` view class.

See #27016.


Built from https://develop.svn.wordpress.org/trunk@27440


git-svn-id: http://core.svn.wordpress.org/trunk@27287 1a063a9b-81f0-0310-95a4-ce76da25c4cd