[TASK] Protect ImportExportController

To gain freedom in v10 refactoring this controller, the class
no longer extends BaseScriptClass, copies over properties and
methods from the base class and sets them to protected.

Resolves: #85031
Releases: master
Change-Id: I3c71ede5f2e00e93b5dc5cd0c9c540540d7e5058
Reviewed-on: https://review.typo3.org/58228


Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>