Make RenderTextures explicitly linear

Assets/ScriptableRenderLoop/HDRenderPipeline/Material/Lit/Lit.cs

                 m_InitPreFGD = CreateEngineMaterial("Hidden/HDRenderPipeline/PreIntegratedFGD");
 
                 // TODO: switch to RGBA64 when it becomes available.
-                m_PreIntegratedFGD = new RenderTexture(128, 128, 0, RenderTextureFormat.ARGBHalf);
+                m_PreIntegratedFGD = new RenderTexture(128, 128, 0, RenderTextureFormat.ARGBHalf, RenderTextureReadWrite.Linear);
 
                 m_LtcGGXMatrix                    = LoadLUT(TextureFormat.RGBAHalf, s_LtcGGXMatrixData);
                 m_LtcDisneyDiffuseMatrix          = LoadLUT(TextureFormat.RGBAHalf, s_LtcDisneyDiffuseMatrixData);

Assets/ScriptableRenderLoop/HDRenderPipeline/Sky/RuntimeFilterIBL.cs

 
             if (!m_GgxIblSampleData)
             {
-                m_GgxIblSampleData = new RenderTexture(k_GgxIblMaxSampleCount, k_GgxIblMipCountMinusOne, 0, RenderTextureFormat.ARGBFloat);
+                m_GgxIblSampleData = new RenderTexture(k_GgxIblMaxSampleCount, k_GgxIblMipCountMinusOne, 0, RenderTextureFormat.ARGBFloat, RenderTextureReadWrite.Linear);
                 m_GgxIblSampleData.useMipMap = false;
                 m_GgxIblSampleData.autoGenerateMips = false;
                 m_GgxIblSampleData.enableRandomWrite = true;

Assets/ScriptableRenderLoop/HDRenderPipeline/Sky/SkyManager.cs

 
             if (m_SkyboxCubemapRT == null)
             {
-                m_SkyboxCubemapRT = new RenderTexture(resolution, resolution, 0, RenderTextureFormat.ARGBHalf);
+                m_SkyboxCubemapRT = new RenderTexture(resolution, resolution, 0, RenderTextureFormat.ARGBHalf, RenderTextureReadWrite.Linear);
                 m_SkyboxCubemapRT.dimension = TextureDimension.Cube;
                 m_SkyboxCubemapRT.useMipMap = true;
                 m_SkyboxCubemapRT.autoGenerateMips = true; // Generate regular mipmap for filtered importance sampling
-                m_SkyboxGGXCubemapRT = new RenderTexture(resolution, resolution, 0, RenderTextureFormat.ARGBHalf);
+                m_SkyboxGGXCubemapRT = new RenderTexture(resolution, resolution, 0, RenderTextureFormat.ARGBHalf, RenderTextureReadWrite.Linear);
                 m_SkyboxGGXCubemapRT.dimension = TextureDimension.Cube;
                 m_SkyboxGGXCubemapRT.useMipMap = true;
                 m_SkyboxGGXCubemapRT.autoGenerateMips = false;
                     int height = (int)LightSamplingParameters.TextureHeight;
 
                     // + 1 because we store the value of the integral of the cubemap at the end of the texture.
-                    m_SkyboxMarginalRowCdfRT = new RenderTexture(height + 1, 1, 0, RenderTextureFormat.RFloat);
+                    m_SkyboxMarginalRowCdfRT = new RenderTexture(height + 1, 1, 0, RenderTextureFormat.RFloat, RenderTextureReadWrite.Linear);
                     m_SkyboxMarginalRowCdfRT.useMipMap = false;
                     m_SkyboxMarginalRowCdfRT.autoGenerateMips = false;
                     m_SkyboxMarginalRowCdfRT.enableRandomWrite = true;
                     // TODO: switch the format to R16 (once it's available) to save some bandwidth.
-                    m_SkyboxConditionalCdfRT = new RenderTexture(width, height, 0, RenderTextureFormat.RFloat);
+                    m_SkyboxConditionalCdfRT = new RenderTexture(width, height, 0, RenderTextureFormat.RFloat, RenderTextureReadWrite.Linear);
                     m_SkyboxConditionalCdfRT.useMipMap = false;
                     m_SkyboxConditionalCdfRT.autoGenerateMips = false;
                     m_SkyboxConditionalCdfRT.enableRandomWrite = true;