Universal 3D (Core) support

In order to support Universal 3D (Core) SRP template, we just need to enable these Render pipeline settings

• Project Settings > Graphics > Default Render Pipeline > "Mobile_RPAsset"

• Go to Player Settings -> XR Plugin Management and enable Google ARCore or Apple ARKit.

• Select "Mobile_Renderer" from Assets > Settings - now in the Inspector panel: click on "Add Render Feature" and select "AR Background Renderer Feature".