Generate stereo and forward-rendering state in HDCamera

Stereo is enabled on a per-camera basis, if stereo is generally active and the camera can render to both eyes.

Additionally, the HDCamera itself will start storing the forward-only state as stereo rendering will be forward only for HDRP (for now).

ScriptableRenderPipeline/HDRenderPipeline/Camera/HDCamera.cs

         // avoid one-frame jumps/hiccups with temporal effects (motion blur, TAA...)
         public bool isFirstFrame { get; private set; }
 
+        public bool useForwardOnly { get; private set; }
+        public bool stereoEnabled { get; private set; }
+
         public Vector4 invProjParam
         {
             // Ref: An Efficient Depth Linearization Method for Oblique View Frustums, Eq. 6.
             Reset();
         }
 
-        public void Update(PostProcessLayer postProcessLayer)
+        public void Update(PostProcessLayer postProcessLayer, GlobalRenderingSettings globalRenderingSettings, bool stereoActive)
         {
             // If TAA is enabled projMatrix will hold a jittered projection matrix. The original,
             // non-jittered projection matrix can be accessed via nonJitteredProjMatrix.
             frustumPlaneEquations[5] = new Vector4(-camera.transform.forward.x, -camera.transform.forward.y, -camera.transform.forward.z,  Vector3.Dot(camera.transform.forward, relPos) + camera.farClipPlane);
 
             m_LastFrameActive = Time.frameCount;
+
+            stereoEnabled = stereoActive && (camera.stereoTargetEye == StereoTargetEyeMask.Both);
+            useForwardOnly = globalRenderingSettings.ShouldUseForwardRenderingOnly() || stereoEnabled;
         }
 
         public void Reset()
+            stereoEnabled = false;
+            useForwardOnly = false;
-        public static HDCamera Get(Camera camera, PostProcessLayer postProcessLayer)
+        public static HDCamera Get(Camera camera, PostProcessLayer postProcessLayer, GlobalRenderingSettings globalRenderingSettings, bool stereoActive)
         {
             HDCamera hdcam;
 
                 s_Cameras.Add(camera, hdcam);
             }
 
-            hdcam.Update(postProcessLayer);
+            hdcam.Update(postProcessLayer, globalRenderingSettings, stereoActive);
             return hdcam;
         }
 

ScriptableRenderPipeline/HDRenderPipeline/HDRenderPipeline.cs

                 m_FrameCount = Time.frameCount;
             }
 
-            var stereoEnabled = UnityEngine.XR.XRSettings.isDeviceActive && m_CurrentDebugDisplaySettings.renderingDebugSettings.allowStereo;
+            var stereoActive = UnityEngine.XR.XRSettings.isDeviceActive && m_CurrentDebugDisplaySettings.renderingDebugSettings.allowStereo;
 
             foreach (var camera in cameras)
             {
             renderContext.SetupCameraProperties(camera);
 
             var postProcessLayer = camera.GetComponent<PostProcessLayer>();
-            var hdCamera = HDCamera.Get(camera, postProcessLayer);
+            var hdCamera = HDCamera.Get(camera, postProcessLayer, m_Asset.globalRenderingSettings, stereoActive);
             PushGlobalParams(hdCamera, cmd, sssSettings);
 
             // TODO: Find a correct place to bind these material textures