[TASK] Streamline DataHandler functional tests

* load modified typo3conf/extTables.php
* add label for copied records
* add label for localized records
* streamline test assertion of IRRE reference test

Resolves: #56029
Releases: 6.2
Change-Id: I4b60200c568aa17e8d51cae95567fe045bff62c7
Reviewed-on: https://review.typo3.org/27648
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader