[TASK] Include all classes via use statements in ext:backend

This patch has been created with rector and php-cs-fixer

    bin/rector process --set=php53 typo3/sysext/backend/Classes
    bin/rector process --set=php53 typo3/sysext/backend/Tests

Releases: master
Resolves: #91064
Change-Id: I9e91882ab233b0e34bc991fd348fceba197a91ea
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/64187


Tested-by: Benni Mack <benni@typo3.org>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>