TinyMCE views: fix Firefox issues.

* Set focus before rendering to prevent reload in Firefox.
* Rerender views if they are unloaded.
* Remove timeout added in [29513].
* Fix argument in wp.mce.views.render.
* Empty views on hide. Missed in #36434.

Props gitlost, azaozz, iseulde.
Fixes #38511.


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git-svn-id: https://core.svn.wordpress.org/trunk@39222 1a063a9b-81f0-0310-95a4-ce76da25c4cd