Ensure "GFX/processor_effects" is a true boolean as suggested in
the settings module and silently migrate integer/string values
accordingly.

Resolves: #83591
Releases: master
Change-Id: I006e907e75e273009333363a4d42661183ba8721
Reviewed-on: https://review.typo3.org/57391


Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: TYPO3com <no-reply@typo3.com>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Frans Saris <franssaris@gmail.com>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>