[CLEANUP] Introduce getters for globals in BackendUtility

Resolves: #62414
Releases: master
Change-Id: I5f77e85e59a014eeb86fd9ee4db839679c0eac98
Reviewed-on: http://review.typo3.org/33479
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>