Support the `autoplay` attribute, even when the plugin type for a MediaElement instance is Flash. In the media modal, `wp.media.view.VideoDetails` and `wp.media.view.AudioDetails` now extend a unified `wp.media.view.MediaDetails` class which contains all of the player creation and destruction logic. The `remove()` method mimics the `mejs.MediaElementPlayer.remove()` method, but does not re-add the audio/video tag to the DOM. The MEjs method is especially problematic when the tag has `autoplay="true"` and the view has been detached but not destroyed.

Fixes #25077.
See #27016.



git-svn-id: https://develop.svn.wordpress.org/trunk@27450 602fd350-edb4-49c9-b593-d223f7449a82