[TASK] Make AJAX request abortion easier

The AJAX API doesn't expose the AbortController anymore as it has no
benefit for a developer, besides aborting a request. For this reason, the
AJAX API removes the `getAbort()` method and replaces it with an
`abort()` method, which utilizes the controller directly.

Resolves: #90292
Releases: master
Change-Id: Id6355663bc00bbb763692ca3b7fab145cb8cc55e
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/63141


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>