Universal/light layers (#3677)

* Initial light layer support.

* Updated changelog.

* Auto-formatting.

* Update com.unity.render-pipelines.universal/CHANGELOG.md

Co-authored-by: Peter Bay Bastian <pbbastian@users.noreply.github.com>

* Minor fixes.

* Adjusted code to compile out IsMatchingLightLayer() when light layers are disabled (confirmed the code is compiled out on Switch).

* Refactoring.
Fixed small bug with gbuffer index calculation when shadowMask and lightLayers are enabled.
Updated comment for unity_RenderingLayer.

* Added test scenes for light layers (148_Lighting_LightLayers and 148_Lighting_LightLayers_deferred).

* Formating.

* Disable filtering for lightmaps.

* Added 148_Lighting_LightLayers and 148_Lighting_LightLayers_deferred in list of scenes to build and test.

* AdditionalLightData is now unconditionally created when OnEnable() is called, removed unecessary code to create it when light layers are enabled.

* Added some reference images.

* Added fake quality level that references UniversalRPAssetLightLayers.asset as a workaround for ShaderPreprocessor otherwise stripping too much.

* Moved UI element for light layer mask in Light inspector.
Renamed linkLightLayer for shadow to customShadowLayer.

* Detect invalid platforms (GLES2) and display error message.

* More reference images.

* Reference images.

* Wait for 2 frames before taking screenshots. This fixes the test scenes failing on Android GLES3.

* Reference images.

* Tweaked error message.

* Removed duplicate assets.

* Updated UX to match HDRP.
SwapPipelineAsset file redirected to new path.

* Fixed null reference in Player mode.

* Update com.unity.render-pipelines.universal/Runtime/DeferredLights.cs

Fixed typo in comment.

Co-authored-by: Felipe Lira <felipedrl@gmail.com>

* Added comment.

* Moved rendering layer texture from 32 to 8 bits as currently only light layers are stored inside.

* A lot of internal renaming from lightLayers to layerMask.

* Hide light layers for baked lights.

* Fixed formatting to pass yamato format test.

* Terrain vertex lit ignores light layers (because default vertex lit code does so too).
Added missing "instancing_options renderinglayer" to terrain shaders.

* More missing instancing_option renderinglayer.

* Temporarily sable 153_Lighting_EnlightenTerrain.unity because it is broken on iOS device with light layer shader variant addition.

Co-authored-by: Peter Bay Bastian <pbbastian@users.noreply.github.com>
Co-authored-by: Felipe Lira <felipedrl@gmail.com>

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