Screen Space decals do not take light cookies into account when using forward

Screen space decals only sample shadow maps to determine attenuation. The light cookie atlas should also be sampled. 

Steps to repro:

1. Open attached repro project.
2. Enter play mode
3. Observe the red paint decals

Expected: Decals only receive light in the same areas that the regular surfaces do

Actual: Decals seem way too bright since the cookies (which mask out a lot of light) are ignored

This goes for both additional lights and main light even though repro project only uses additional lights