[BUGFIX] Allow any navigation component to load in BE

Since the ExtJS viewport refactoring in 8.5, it is not possible
anymore to load any other registered navigation component,
which makes EXT:commerce to not work anymore.

The patch changes the hard-coded pagetree app component
to fetch it from the pool of available navigation components.

Resolves: #80058
Releases: master
Change-Id: I1ce4cfa068f72f39cd5d993df6f9ebbdb7d07b2e
Reviewed-on: https://review.typo3.org/51888


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Thomas Maroschik <tmaroschik@dfau.de>
Tested-by: Thomas Maroschik <tmaroschik@dfau.de>
Reviewed-by: Sebastian Fischer <typo3@evoweb.de>
Tested-by: Sebastian Fischer <typo3@evoweb.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>