The LocalizationController used by the localization wizard is
now covered by some functional tests.
For better testability, the DataHandler processing in the
controller is moved into its own method.

Resolves: #75160
Related: #73617
Releases: master, 7.6
Change-Id: I3275f51d3dfec55ace3d8dbe7130c3f18b963341
Reviewed-on: https://review.typo3.org/47305


Reviewed-by: Nicole Cordes <typo3@cordes.co>
Tested-by: Nicole Cordes <typo3@cordes.co>
Reviewed-by: Steffen Müller <typo3@t3node.com>
Tested-by: Steffen Müller <typo3@t3node.com>