[BUGFIX] Check minitems for TCAtree

The TCAtree ignores currently the minitems.
This is however e.g. needed to require input for a relation field.

Change-Id: I41b345f19f845a8b31e791c11a7c4a907d499ad5
Resolves: #25003
Releases: 4.7, 4.6, 4.5
Reviewed-on: https://review.typo3.org/12797
Reviewed-by: Wouter Wolters
Reviewed-by: Marcus Schwemer
Tested-by: Marcus Schwemer
Reviewed-by: Stefan Neufeind
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader