Make `CollectionEdit` and `CollectionAdd` less dynamically quirky. Rename some instance properties for disambiguation. Pass some properties from `options` when creating instances in `wp.media.view.MediaFrame.Post`.

See #26631.
Props gcorne.



git-svn-id: https://develop.svn.wordpress.org/trunk@27362 602fd350-edb4-49c9-b593-d223f7449a82
Adjust the priority of the separator in the Edit Playlist and Edit Video Playlist menus to match the structure of the Edit Gallery menu.

Props gcorne.
See #26631.



git-svn-id: https://develop.svn.wordpress.org/trunk@27363 602fd350-edb4-49c9-b593-d223f7449a82