[TASK] RTE: Migrate outer editor framework to plain JavaScript

Replace the extended Ext.Container with plain JavaScript.
Use jQuery UI Resizable in replacement of Ext.Resizable.

Releases: master
Resolves: #63757
Change-Id: I86625b28228c30cdb7524f49014101a40351d17e
Reviewed-on: http://review.typo3.org/35277
Reviewed-by: Stanislas Rolland <typo3@sjbr.ca>
Tested-by: Stanislas Rolland <typo3@sjbr.ca>