Add a timestamp to the urls passed to `<audio>` and `<video>` in the modal to ensure that cached view instances aren't referenced by MEjs. Pause the player when closing the controller's modal.

See #27016, #26779.


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Ensure that all a/v attribute names have a leading space when the tags are dynamically-generated via Underscore templates.

See #27016.


Built from https://develop.svn.wordpress.org/trunk@27421


git-svn-id: http://core.svn.wordpress.org/trunk@27268 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Update the list of HTTP status code descriptions. Fixes #16914. Props sirzooro and hakre for the original patches.
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