Add high level camera callbacks to HD / LW.

ScriptableRenderPipeline/HDRenderPipeline/HDRP/HDRenderPipeline.cs

-using System.Collections.Generic;
+using System.Collections.Generic;
 using UnityEngine.Rendering;
 using System;
 using System.Diagnostics;
         public override void Render(ScriptableRenderContext renderContext, Camera[] cameras)
         {
             base.Render(renderContext, cameras);
+            BeginFrameRendering(cameras);
 
             if (m_FrameCount != Time.frameCount)
             {
             {
                 if (camera == null)
                     continue;
+
+                BeginCameraRendering(camera);
 
                 if (camera.cameraType != CameraType.Reflection)
                     // TODO: Render only visible probes

ScriptableRenderPipeline/LightweightPipeline/LWRP/LightweightPipeline.cs

         public override void Render(ScriptableRenderContext context, Camera[] cameras)
         {
             base.Render(context, cameras);
+            BeginFrameRendering(cameras);
 
             GraphicsSettings.lightsUseLinearIntensity = true;
             SetupPerFrameShaderConstants();
             foreach (Camera camera in cameras)
             {
+                BeginCameraRendering(camera);
+
                 bool sceneViewCamera = camera.cameraType == CameraType.SceneView;
                 bool stereoEnabled = XRSettings.isDeviceActive && !sceneViewCamera;
                 m_CurrCamera = camera;