[TASK] FormEngine: Test FlexForm sheet displayCond with logical operator

Add unit test to test that logical operator work in displayCond at the
level of FlexForm sheets.

Resolves: #68989
Releases: master
Change-Id: I2f6d7359ee742a8738c2aaacf41193c506bdad82
Reviewed-on: https://review.typo3.org/45366


Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>