[TASK] Usability improvements for scheduler module

This patch add another icon for the „run on next cron“ button and add 
tooltips for a better and faster understanding of the buttons.

Resolves: #79695
Related: #45537
Releases: master
Change-Id: I0ba372f2f884af22c1f4fd74be99208493624971
Reviewed-on: https://review.typo3.org/51598


Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: TYPO3com <no-reply@typo3.com>
Tested-by: Mona Muzaffar <mona.muzaffar@gmx.de>
Reviewed-by: Mona Muzaffar <mona.muzaffar@gmx.de>
Reviewed-by: Tymoteusz Motylewski <t.motylewski@gmail.com>
Tested-by: Tymoteusz Motylewski <t.motylewski@gmail.com>