Media Grid: remove some unused Trash/Delete handler logic. Rendered useless since [29266] and made official by [29322].

See #28819.

Built from https://develop.svn.wordpress.org/trunk@29427


git-svn-id: http://core.svn.wordpress.org/trunk@29205 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Media Grid: add screen reader labels with more context to filters and bulk actions. Ditto for list view.

Props afercia.
Fixes #29026.

Built from https://develop.svn.wordpress.org/trunk@29428


git-svn-id: http://core.svn.wordpress.org/trunk@29206 1a063a9b-81f0-0310-95a4-ce76da25c4cd
MediaElement upgrade: cleanup for generated markup for videos. 

See #29110.

Built from https://develop.svn.wordpress.org/trunk@29429


git-svn-id: http://core.svn.wordpress.org/trunk@29207 1a063a9b-81f0-0310-95a4-ce76da25c4cd