Move Fast Gi Ambient Occlusion to AO Pass

Currently when enabling Raytracing+Fast Gi and switching the approximation method from Global Illumination to Ambient Occlusion, the occlusion is combined into both direct passes and cannot be seen in the Ambient Occlusion Pass. This makes editing just the AO in post/compositor "impossible".

Fix: Make it so the Fast GI Ambient occlusion appears in the Ambient Occlusion Pass, NOT combined in the direct passes.