Add SPR Batcher support

[unitycoder]

For a custom shader to be compatible with the SRP Batcher it must meet the following requirements:

• The shader must declare all built-in engine properties in a single constant buffer named UnityPerDraw. For example, unity_ObjectToWorld, or unity_SHAr.
• The shader must declare all material properties in a single constant buffer named UnityPerMaterial.

https://docs.unity3d.com/Manual/SRPBatcher.html