Audio/Video shortcodes in the media modal:

* Add `embedMimes` to `_wpMediaViewsL10n`
* Use `escape` instead of `interpolate` when setting attributes in Underscore templates
* When creating the `<audio>` and `<video>` tags dynamically, set inner `<source>` nodes instead of the `src` attribute and properly set the mime-type per source as the `type` attribute. This is also drastically reduces the amount of code used to generate the tags.

See #27016.



git-svn-id: https://develop.svn.wordpress.org/trunk@27476 602fd350-edb4-49c9-b593-d223f7449a82
In `wp.media.model.PostAudio` and `wp.media.model.PostVideo`, use Underscore's `unset` method when clearing out properties when the attachment changes.

See #27016.



git-svn-id: https://develop.svn.wordpress.org/trunk@27477 602fd350-edb4-49c9-b593-d223f7449a82