[TASK] Style pagetree icons

In order to streamline the icons
in the pagetree as well, another
signal is introduced to change
items when only CSS classes
are built within IconUtility.

For the topbar of the pagetree
certain hover states are
removed and streamlined.

Releases: master
Resolves: #63137
Change-Id: Id273cbf0f86a27eafe1a75d6611643703b4290ee
Reviewed-on: http://review.typo3.org/34463
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Frank Nägler <typo3@naegler.net>
Tested-by: Frank Nägler <typo3@naegler.net>