[FEATURE] Change wizard icon generation

Change the generation of the new content element wizard from
php file to page typoscript

Releases: 6.2
Change-Id: Ia091b8d801a592da6d1bfde64a74a8f11f5ad3ad
Reviewed-on: https://review.typo3.org/24616
Reviewed-by: Sebastian Fischer
Tested-by: Sebastian Fischer