[BUGFIX] SplitButtons: Abort click event if requested

If any callback is registered by `SplitButtons.addPreSubmitCallback()` and
requests to stop the event by `stopPropagation()`, the event must be
aborted and not only possibly stacked events.
Additionally, the `preventExec` flag gets reset.

Resolves: #82355
Related: #77942
Releases: master, 8.7, 7.6
Change-Id: Ib8478ef4c51915365c804c1c408b3fc16a13da0b
Reviewed-on: https://review.typo3.org/53968


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Matthias Vogel <typo3@kanti.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>