Add sRGB support for color picker debug

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Debug/DebugColorPicker.shader

             #pragma fragment Frag
 
             #include "CoreRP/ShaderLibrary/Common.hlsl"
+            #include "CoreRP/ShaderLibrary/Color.hlsl"
             #include "../ShaderVariables.hlsl"
             #include "../Debug/DebugDisplay.cs.hlsl"
             #include "../Debug/DebugDisplay.hlsl"
             float4 _ColorPickerParam; // 4 increasing threshold
             int _ColorPickerMode;
             float3 _ColorPickerFontColor;
+            float _ApplyLinearToSRGB;
 
             struct Attributes
             {
             {
                 if (_MousePixelCoord.z >= 0.0 && _MousePixelCoord.z <= 1.0 && _MousePixelCoord.w >= 0 && _MousePixelCoord.w <= 1.0)
                 {
+                    // As when we read with the color picker we don't go through the final blit (that current hardcode a conversion to sRGB)
+                    // and as our material debug take it into account, we need to a transform here.
+                    if (_ApplyLinearToSRGB > 0.0)
+                    {
+                        mouseResult.rgb = LinearToSRGB(mouseResult.rgb);
+                    }
+
                     // Display message offset:
                     int displayTextOffsetX = 1.5 * DEBUG_FONT_TEXT_WIDTH;
                     #if UNITY_UV_STARTS_AT_TOP

ScriptableRenderPipeline/HDRenderPipeline/HDRP/HDRenderPipeline.cs

                     var colorPickerParam = new Vector4(colorPickerDebugSettings.colorThreshold0, colorPickerDebugSettings.colorThreshold1, colorPickerDebugSettings.colorThreshold2, colorPickerDebugSettings.colorThreshold3);
                     m_DebugColorPicker.SetVector(HDShaderIDs._ColorPickerParam, colorPickerParam);
                     m_DebugColorPicker.SetInt(HDShaderIDs._ColorPickerMode, (int)colorPickerDebugSettings.colorPickerMode);
+                    // The material display debug perform sRGBToLinear conversion as the final blit currently hardcode a linearToSrgb conversion. As when we read with color picker this is not done,
+                    // we perform it inside the color picker shader. But we shouldn't do it for HDR buffer.
+                    m_DebugColorPicker.SetFloat(HDShaderIDs._ApplyLinearToSRGB, m_CurrentDebugDisplaySettings.IsDebugMaterialDisplayEnabled() ? 1.0f : 0.0f);
 
                     CoreUtils.DrawFullScreen(cmd, m_DebugColorPicker, (RenderTargetIdentifier)BuiltinRenderTextureType.CameraTarget);
                 }

ScriptableRenderPipeline/HDRenderPipeline/HDRP/HDStringConstants.cs

         public static readonly int _DebugColorPickerTexture = Shader.PropertyToID("_DebugColorPickerTexture");
         public static readonly int _ColorPickerParam = Shader.PropertyToID("_ColorPickerParam");
         public static readonly int _ColorPickerMode = Shader.PropertyToID("_ColorPickerMode");
+        public static readonly int _ApplyLinearToSRGB = Shader.PropertyToID("_ApplyLinearToSRGB");
         public static readonly int _ColorPickerFontColor = Shader.PropertyToID("_ColorPickerFontColor");
 
         public static readonly int _DebugFullScreenTexture = Shader.PropertyToID("_DebugFullScreenTexture");