[TASK] Introduced getter for $GLOBALS in backend/Classes/ContextMenu

- add getter for LanguageService
- add getter for BackendUser

Resolves: #65445
Releases: master
Change-Id: I985f9b0aa619ea7f90f35fe169122c26850a73df
Reviewed-on: http://review.typo3.org/37444


Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>