[TASK] Doctrine: migrate ext:backend/Backend/ToolbarItems

Releases: master
Resolves: #75697
Change-Id: I9105289b14a3c2dba07275ff2690291c5cfba508
Reviewed-on: https://review.typo3.org/47719


Reviewed-by: Frank Naegler <frank.naegler@typo3.org>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Peter Foerger <pfoerger@mac.com>
Tested-by: Peter Foerger <pfoerger@mac.com>
Reviewed-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Tested-by: Morton Jonuschat <m.jonuschat@mojocode.de>