Iris core sharers compat fix

This is a small and experimental mod that attempts making iris behave and not completely nuke all custom core shaders added by mods.

Normally when iris shaderpacks are active, object rendered via custom shaders added by mods will render completely black.

With this on they should render, ideally more or less right.

This mod internals are not perfect nor pretty but they dont have to be. It was born out of necessity and works in most cases i tested.