[TASK] RTE: Migrate status bar to plain JavaScript

The status bar is plain JavaScript but still uses Ext.QuickTips markup.

Releases: master
Resolves: #63760
Change-Id: I1aafc0d0b87db198132c26a214950470368cb69f
Reviewed-on: http://review.typo3.org/35282
Reviewed-by: Stanislas Rolland <typo3@sjbr.ca>
Tested-by: Stanislas Rolland <typo3@sjbr.ca>