[!!!][TASK] Trees do not use global SOBE anymore

The back-reference to the underlying instance of ElementBrowser is now
stored as member of the tree.

Resolves: #69276
Releases: master
Change-Id: Ie48a77cd01269ea7e13905d651663424dbb616a1
Reviewed-on: http://review.typo3.org/42853


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Alexander Opitz <opitz.alexander@googlemail.com>
Tested-by: Alexander Opitz <opitz.alexander@googlemail.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>