[TASK] Use a new icon for sys_action toolbar

The sysaction icon in the toolbar must also be changed to an icon
of font awesome.

Resolves: #62315
Releases: master
Change-Id: I8fe101948affaaa1e98778784572775d5380b6cc
Reviewed-on: http://review.typo3.org/33372
Reviewed-by: Kay Strobach <typo3@kay-strobach.de>
Tested-by: Kay Strobach <typo3@kay-strobach.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>