[TASK] RTE: Simplify editor framework

Simplify RTE framework from Ext.panel to Ext.Container.
Reduce dependency on Ext.ComponentMgr.registerType

Releases: master
Resolves: #63723
Change-Id: I466fa37897e3db97350a7116ce1c3c0be17a6941
Reviewed-on: http://review.typo3.org/35212
Reviewed-by: Stanislas Rolland <typo3@sjbr.ca>
Tested-by: Stanislas Rolland <typo3@sjbr.ca>