[!!!][TASK] Remove legacy TreeView functionality

Removed classes:
* TYPO3\CMS\Backend\Tree\View\BrowseTreeView
* TYPO3\CMS\Backend\Tree\View\ElementBrowserPageTreeView

Removed methods:
* TYPO3\CMS\Backend\Tree\View\AbstractTreeView->determineScriptUrl
* TYPO3\CMS\Backend\Tree\View\AbstractTreeView->getThisScript
* TYPO3\CMS\Backend\Tree\View\AbstractTreeView->addTagAttributes
* TYPO3\CMS\Backend\Tree\View\AbstractTreeView->getRootIcon
* TYPO3\CMS\Backend\Tree\View\AbstractTreeView->getRootRecord

Removed properties:
* TYPO3\CMS\Backend\Tree\View\AbstractTreeView->thisScript
* TYPO3\CMS\Backend\Tree\View\AbstractTreeView->BE_USER

Various other properties / methods which have been marked as
internal are now properly set as protected.

Resolves: #101072
Related: #100963
Related: #100454
Releases: main
Change-Id: I1348fef4bd2b0093b7d0424891f7924bb86b3019
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/79267


Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>