Add functional tests for tt_content rendering
with different combinations of TypoScript language
settings sys_language_overlay and sys_language_mode.

Resolves: #81185
Releases: master, 8.7
Change-Id: I7df5b48a2baa3a52f8c6103b0657b21226c6ea5c
Reviewed-on: https://review.typo3.org/52750


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>