Change normal slot in PBR Master node to display default space binding rather than a vector3 control

com.unity.shadergraph/Editor/Data/Graphs/NormalMaterialSlot.cs

 namespace UnityEditor.ShaderGraph
 {
     [Serializable]
-    public class NormalMaterialSlot : SpaceMaterialSlot, IMayRequireNormal
+    public class NormalMaterialSlot : SpaceMaterialSlot, IMayRequireNormal, IMayRequireTangent
     {
         public NormalMaterialSlot()
         {}
         }
 
         public NeededCoordinateSpace RequiresNormal()
+        {
+            if (isConnected)
+                return NeededCoordinateSpace.None;
+            return space.ToNeededCoordinateSpace();
+        }
+        public NeededCoordinateSpace RequiresTangent()
         {
             if (isConnected)
                 return NeededCoordinateSpace.None;

com.unity.shadergraph/Editor/Data/MasterNodes/PBRMasterNode.cs

         {
             name = "PBR Master";
             AddSlot(new ColorRGBMaterialSlot(AlbedoSlotId, AlbedoSlotName, AlbedoSlotName, SlotType.Input, Color.grey, ShaderStage.Fragment));
-            AddSlot(new Vector3MaterialSlot(NormalSlotId, NormalSlotName, NormalSlotName, SlotType.Input, new Vector3(0, 0, 1), ShaderStage.Fragment));
+            AddSlot(new NormalMaterialSlot(NormalSlotId, NormalSlotName, NormalSlotName, CoordinateSpace.Tangent, ShaderStage.Fragment));
             AddSlot(new ColorRGBMaterialSlot(EmissionSlotId, EmissionSlotName, EmissionSlotName, SlotType.Input, Color.black, ShaderStage.Fragment));
             if (model == Model.Metallic)
                 AddSlot(new Vector1MaterialSlot(MetallicSlotId, MetallicSlotName, MetallicSlotName, SlotType.Input, 0, ShaderStage.Fragment));