[TASK] Speed up page tree loading

Instead of doing manual queries for each tree level, and checking
for children on each tree level, the page tree now fetches all pages
the user has access to, and checks if this works out.

Resolves: #83233
Releases: master
Change-Id: I45a6b834ef1fe71e5748dfc8de9bcf6dad8172c9
Reviewed-on: https://review.typo3.org/54887


Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>