Literal item overlay patch:
- replaces the previous BakedQuad mutation item mixin implementation
- injects into ItemRenderer.renderItem (method_23179)
- immediately after the base baked model render, draws the actual scar/parasite/sparkle PNG as a second textured quad
- draws front and back faces so GUI, held, fixed and dropped/rotating items can display the mask
- does not rely on renderBakedItemQuads locals or tinting
