Load default settings state when creating a new playlist in the media modal. Add a few missing inline `@this` annotations in `media-editor.js`.

See #26631.


Built from https://develop.svn.wordpress.org/trunk@27242


git-svn-id: http://core.svn.wordpress.org/trunk@27099 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Remove a few unnecessary jQuery selectors added in [27239]. Playlists don't exist in some older contexts that galleries do.

See #26631.


Built from https://develop.svn.wordpress.org/trunk@27243


git-svn-id: http://core.svn.wordpress.org/trunk@27100 1a063a9b-81f0-0310-95a4-ce76da25c4cd