Resolved URP Render Objects support for Rendering Layers

There was some movement on this here
https://forum.unity.com/threads/ren...sing-support-for-rendering-layer-mask.867391/

Here is the last pull request I know of with any movement on this before it was shelved:
https://github.com/Unity-Technologies/Graphics/pull/1891

It seemed to have been shelved because the URP team was trying to figure out how to make it work with shadows and such.

I think it would be useful to have even if it didn't work with lighting systems.

Using RenderObjects for an Occlusion Effect is a common example:
https://github.com/Unity-Technologies/UniversalRenderingExamples/wiki/Occlusion

If we were allowed to specify Render Layer's in the RenderObject's pass then we could dedicate certain layers to be for certain effects.

For example, in my project RenderingLayer 25 could be for the Occlusion Effect. RenderingLayer 26 could be for Outline effect. RenderingLayer 27 could be for SomeOtherCoolEffect.

Now any MeshRenderer in the game can 'opt in' to be a part of any number of my effects! I just have to include it in the appropriate RenderingLayer. This is easy to control at runtime too. IE when the cursor hovers over an object, add RenderLayer 26 to its RenderingLayerMask and boom - outline effect around the item your cursor is hovering over..!