[BUGFIX] Fix placeholder type detection

Fix the detection of object storages and boolean values in the
TYPO3 database backend for Extbase.

The getPlainValue method is consolidated in the DataMapper and will
not throw an Exception for arrays any more but will convert multi
value objects or arrays to a comma seperated value list that can be
used in IN queries.

Resolves: #57104
Releases: 6.2
Change-Id: Ic35fd2768a1431f260c99d6faf8ad4e0a1754ea3