Fake Additional Lights

[Delt06]

Similar to blob shadows, this should draw additional lights into a separate low-res texture.
As an authoring tool, we can still use the built-in light component.

Pass a uniform light array (can't use the already existing one since it assumes the usual additional lights are disabled).

Create a shader graph sub graph:

• Takes albedo and occlusion value, outputs the color sample, to be plugged into the emission field.
• Idea: input blob shadow samples into the occlusion value

Support several light types:

• Point
  • Tighter meshes based on plane/sphere section radius
• Spot?
  • Tighter meshes for spot lights: won't do, vertex shader will be too complicated if we want to keep it tigher than the quad approach
• Distance fade
• Height fade
• Optionally apply the global ramp or use other threshold+smoothness values
• Change property strings to IDs
• Make sub graph output distance attenuation - for custom ramp computation
• Cull lights
  • By Y
  • By camera distance
• Optimize light collection
• Test on WebGL with non-full batches
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