[REVERT] Use TYPO3 DataHandler in the backend

[sebastian-meyer]

Since introducing support for TYPO3 v11, all data processes were rewritten to use the Doctrine DBAL directly. While this is good for all (reading) frontend queries, it's quite problematic for the (writing) backend processes. Especially sorting and translating of records in the backend list module does not work correctly (see #1147, #1182, #1183).

Some workarounds have been introduced to fix the problem in the short-term (see #1169, #1184, #1186), but a proper fix would be to revert to using the TYPO3 DataHandler in the backend.

[sebastian-meyer]

Fixed by #1212.