[TASK] Integrate Pagetree acceptance suite into Backend suite

The Pagetree suite for acceptance tests was set up as a separate
suite in the beginning due to a necessary fixture set of pages,
that all the other tests don't need.
The overhead of having separate suite is higher than the additional
fixture set, so the suites are merged.

Resolves: #93614
Releases: master, 10.4
Change-Id: I70a3f1dd68bb07c0dc505eaadb3d240e81639add
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/68151


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Richard Haeser <richard@richardhaeser.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Richard Haeser <richard@richardhaeser.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>