[BUGFIX] RSA encryption: Stop submit handling if requested

If the submit event of a form using RSA encryption has `cancelBubble` set
to true (e.g. by jQuery's stopPropagation()), any processing is stopped
to prevent submitting the form.

Resolves: #82259
Releases: master, 8.7
Change-Id: Idb357dd2043cccb899ad7fa3fa325f7d3c003e40
Reviewed-on: https://review.typo3.org/53845


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>