Update Changelog and integrate PR feedback

com.unity.render-pipelines.high-definition/CHANGELOG.md

 
 ### Changed
 - Re-enable shadow mask mode in debug view
+- SSS and Transmission code have been refactored to be able to share it between various material. Guidelines are in SubsurfaceScattering.hlsl
 
 ### Fixed
 - Fix contact shadows applied on transmission

com.unity.render-pipelines.high-definition/HDRP/Lighting/LightEvaluation.hlsl

 
 // This function return transmittance to provide to EvaluateTransmission
 float3 PreEvaluatePunctualLightTransmission(LightLoopContext lightLoopContext, PositionInputs posInput, float distFrontFaceToLight,
-                                            float NdotL, float3 L, LightData lightData, BSDFData bsdfData,
-                                            inout float3 normalWS, inout int contactShadowIndex)
+                                            float NdotL, float3 L, BSDFData bsdfData,
+                                            inout float3 normalWS, inout LightData lightData)
 {
     float3 transmittance = bsdfData.transmittance;
 
         if (HasFlag(bsdfData.materialFeatures, MATERIAL_FEATURE_FLAGS_TRANSMISSION_MODE_THIN_THICKNESS))
         {
             normalWS = -normalWS; // Flip normal for shadow bias
-            contactShadowIndex = -1;  //  Disable shadow contact
+            lightData.contactShadowIndex = -1;  //  Disable shadow contact
         }
         else // MATERIAL_FEATURE_FLAGS_TRANSMISSION_MODE_MIXED_THICKNESS
         {

com.unity.render-pipelines.high-definition/HDRP/Material/Lit/Lit.hlsl

     float3 transmittance = float3(0.0, 0.0, 0.0);
     if (HasFlag(bsdfData.materialFeatures, MATERIALFEATUREFLAGS_LIT_TRANSMISSION))
     {
-        // Caution: This function modify N and contactShadowIndex
-        transmittance = PreEvaluatePunctualLightTransmission(lightLoopContext, posInput, distances.x, NdotL, L, lightData, bsdfData, N, lightData.contactShadowIndex);
+        // Caution: This function modify N and lightData.contactShadowIndex
+        transmittance = PreEvaluatePunctualLightTransmission(lightLoopContext, posInput, distances.x, NdotL, L, bsdfData, N, lightData);
     }
 
     float3 color;

com.unity.render-pipelines.high-definition/HDRP/Material/StackLit/StackLit.hlsl

     float3 transmittance = float3(0.0, 0.0, 0.0);
     if (HasFlag(bsdfData.materialFeatures, MATERIALFEATUREFLAGS_STACK_LIT_TRANSMISSION))
     {
-        // Caution: This function modify N and contactShadowIndex
-        transmittance = PreEvaluatePunctualLightTransmission(lightLoopContext, posInput, distances.x, NdotL, L, lightData, bsdfData, shadowBiasNormal, lightData.contactShadowIndex);
+        // Caution: This function modify N and lightData.contactShadowIndex
+        transmittance = PreEvaluatePunctualLightTransmission(lightLoopContext, posInput, distances.x, NdotL, L, bsdfData, shadowBiasNormal, lightData);
     }
 
     float3 color;