Cleanup after [29179]:

* `_WP_Editors::editor_settings()` no longer needs to load MEjs styles
* Make sure each identical shortcode with multiple instances also has an iframe sandbox for each instance
* For the time being, make audio and video shortcodes bypass the loading placeholder to avoid whiplash visually

Props avryl, wonderboymusic.
See #28905.

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DB schema change: Add comment_author_email(10) index.

props tellyworth, pento.
fixes #21435.

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Cleanup after [29179]:

* Cleanup players when the editor is hidden - window scope is unique to each frame
* Add the editor body class to each iframe sandbox
* Remove unneeded code from `wp-mediaelement.js`

See #28905.

Built from https://develop.svn.wordpress.org/trunk@29189


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TinyMCE wpView: add noop() when returning early, fixes #28921
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Cleanup after [29179]:

* Pause players when media is edited via modal
* Remove players on unind
* Account for failure when an empty node is passed to an `mce.view.View`

See #28905.

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Autosave: always expose the `wp.autosave.local` methods, fixes #28924.
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