[FEATURE] Signal for IconUtility html tag manipulation

Registers a signal to EXT:Backend\Utility\IconUtility to manipulate
the generated html code for sprite icons.

Resolves: #61289
Releases: 6.3
Change-Id: Ie61e09b2033114b2258bf14eaaba9e068410bcfc
Reviewed-on: http://review.typo3.org/32542
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Felix Kopp <felix-source@phorax.com>
Tested-by: Felix Kopp <felix-source@phorax.com>
Reviewed-by: Nicole Cordes <typo3@cordes.co>
Tested-by: Nicole Cordes <typo3@cordes.co>