[TASK] Simplify hierarchy logic within AbstractTreeView subclasses

This change simplifies the ExportPageTreeView to extend
from AbstractTreeView directly, making the intermediate subclassing
to BrowseTreeView obsolete.

In addition, several properties which are only used within
ExportPageTreeView are moved into this class, reducing the
actual logic within AbstractTreeView.

Unused properties such as "MOUNTS", "bank" and "stored" are
moved to the respective usage'd subclasses.

Resolves: #94007
Releases: master
Change-Id: Ieba1fd4fa6d8df33d1ebdb047f6d76b1b3413bfb
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/68901


Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>