[TASK] Use AJAX API in context menus

The AJAX API is now used in context menus. This patch also incorporates
a neat ES6 feature to use variables in object keys in a sane way.

Resolves: #90039
Releases: master
Change-Id: Ib0edf1b530a1c059f9ff7937bd16358a07a656ea
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/62791


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Tymoteusz Motylewski <t.motylewski@gmail.com>
Tested-by: Frank Nägler <frank.naegler@typo3.org>
Reviewed-by: Tymoteusz Motylewski <t.motylewski@gmail.com>
Reviewed-by: Frank Nägler <frank.naegler@typo3.org>