In `media-views.js`, add `wp.media.controller.CollectionAdd` and `wp.media.controller.CollectionEdit` to provide an abstraction for Add and Edit screens in the media modal for collection-type things.

There are currently no instances of this. Those will be forthcoming.

See #26631.



git-svn-id: https://develop.svn.wordpress.org/trunk@27214 602fd350-edb4-49c9-b593-d223f7449a82