[BUGFIX] Pass field name variable to flexform DS utility

A field name parameter is not being passed from within
DataHandler when copying a record which has a FlexForm
DF associated with it. This causes dynamic FlexForm DS
definitions to not be able to depend on the field name,
in turn causing the problem that an incorrect DS may be
returned from the DS utility which makes TYPO3 process
the data value incorrectly (for example, not detecting
file fields and processing the values accordingly).

To solve this the $field parameter is passed.

Resolves: #59423
Releases: 6.3, 6.2, 6.1
Change-Id: Icfafd553f76e17ad5db651bb3f5dea52b140dcf7
Reviewed-on: https://review.typo3.org/30633
Reviewed-by: Cedric Ziel
Tested-by: Cedric Ziel
Reviewed-by: Markus Klein
Tested-by: Markus Klein