Show title, album, and artist info for audio files displayed in `WP_Customize_Upload_Control()`.

See #21483.

Built from https://develop.svn.wordpress.org/trunk@30737


git-svn-id: http://core.svn.wordpress.org/trunk@30727 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Add some inline JS docs for Customizer.

See #30469.

Built from https://develop.svn.wordpress.org/trunk@30738


git-svn-id: http://core.svn.wordpress.org/trunk@30728 1a063a9b-81f0-0310-95a4-ce76da25c4cd