HDRP: Move contactShadow from shadow context to light context (fix warning)

com.unity.render-pipelines.core/CoreRP/ShaderLibrary/Shadow/Shadow.hlsl

     StructuredBuffer<ShadowData>    shadowDatas;
     StructuredBuffer<int4>          payloads;
     SHADOWCONTEXT_DECLARE_TEXTURES( SHADOWCONTEXT_MAX_TEX2DARRAY, SHADOWCONTEXT_MAX_TEXCUBEARRAY, SHADOWCONTEXT_MAX_COMPSAMPLER, SHADOWCONTEXT_MAX_SAMPLER )
-    float                           contactShadow;
 };
 
 SHADOW_DEFINE_SAMPLING_FUNCS( SHADOWCONTEXT_MAX_TEX2DARRAY, SHADOWCONTEXT_MAX_TEXCUBEARRAY, SHADOWCONTEXT_MAX_COMPSAMPLER, SHADOWCONTEXT_MAX_SAMPLER )

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

     LightLoopContext context;
     context.sampleReflection = 0;
     context.shadowContext = InitShadowContext();
-
-    context.shadowContext.contactShadow = LOAD_TEXTURE2D(_DeferredShadowTexture, posInput.positionSS).y;
+    context.contactShadow = LOAD_TEXTURE2D(_DeferredShadowTexture, posInput.positionSS).y; // Contactshadow is store in Green Channel of _DeferredShadowTexture
 
     // This struct is define in the material. the Lightloop must not access it
     // PostEvaluateBSDF call at the end will convert Lighting to diffuse and specular lighting

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

 {
     int sampleReflection;
     ShadowContext shadowContext;
+    float contactShadow; // Currently we support only one contact shadow per view
 };
 
 //-----------------------------------------------------------------------------
     // return 1
     // On the other hand, if the feature is active it's value is 0 so we can return
     // the value fetched at the begining of LightLoop()
-    return max(lightLoopContact.shadowContext.contactShadow, abs(contactShadowIndex));
-}
+    return max(lightLoopContact.contactShadow, abs(contactShadowIndex));
+}