Also:
* Reduce the amount of callbacks.
* Move everything under `preinit` (but prepend to the callback). The API shouldn't be availbale earlier, and some UI is not available yet, neither is `editor.dom`.
* Hide the toolbar if the target is out of view.
See #32604.
Built from https://develop.svn.wordpress.org/trunk@32831
git-svn-id: http://core.svn.wordpress.org/trunk@32802 1a063a9b-81f0-0310-95a4-ce76da25c4cd