[BUGFIX] Fix import of type group internal_type file_reference

This patch fixes the import of fields type "group" "internal_type"
"file_reference" and adds functional tests for exporting and
importing records with fields of type "group" "internal_type"
"file" and "file_reference", the types for file handling before
introducing the File Abstraction Layer.

Resolves: #56516
Resolves: #56071
Releases: 6.2
Change-Id: I4298f27ee77a89230188aa0df1b187429d555188
Reviewed-on: https://review.typo3.org/28021
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn