[TASK] Adhere enableDeprecationLog settings

Refactoring of function deprecationLog() to prevent accidental
activation of log file creation due to misconfiguration.
Correct misleading configuration description (label in Install Tool).

Resolves: #43900
Releases: 6.2
Change-Id: I04164270ea3359014b6637d6c68cf2d9348356b0
Reviewed-on: https://review.typo3.org/18510
Reviewed-by: Markus Klein
Tested-by: Markus Klein
Reviewed-by: Alexander Opitz
Reviewed-by: Philipp Gampe
Tested-by: Philipp Gampe