Breaking: #72400 - Removed deprecated IconUtility and SpriteManager 

See forge#72400

Description 

Removed deprecated IconUtility class completely. All SpriteManager related code has been removed from the core.

The Install Tool option BE/spriteIconGenerator_handler has no effect anymore.

Bootstrap::initializeSpriteManager() has been removed.

Impact 

Using the static class IconUtility or the SpriteManager will result in a fatal error.

Affected Installations 

Instances which use custom calls to one of the above mentioned classes.

Migration 

Use the new introduced IconAPI that is available since 7LTS.