[TASK] Use FormDataProvider to provide system-languages

This allows fetching the languages in a central place, including
fetching the default-language name/flag.

Change-Id: I5211bb6fa4ee6df95cb25296b6b35b678d1cc225
Resolves: #70825
Releases: master
Reviewed-on: https://review.typo3.org/44146


Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>