Material Component: Can set material property overrides on default materials

No longer need to assign material overrides to set/edit properties in UI or script
Material component will load and use the default material for a slot if no override is assigned

Signed-off-by: Guthrie Adams <guthadam@amazon.com>

Gems/AtomLyIntegration/CommonFeatures/Code/Source/Material/MaterialComponentController.h

@@ -22,6 +22,7 @@ namespace AZ
         //! to provide material overrides on a per-entity basis.
         class MaterialComponentController final
             : MaterialComponentRequestBus::Handler
+            , MaterialReceiverNotificationBus::Handler
             , Data::AssetBus::MultiHandler
             , TickBus::Handler
         {
@@ -100,6 +101,9 @@ namespace AZ
                 const MaterialAssignmentId& materialAssignmentId, const AZ::RPI::MaterialModelUvOverrideMap& modelUvOverrides) override;
             AZ::RPI::MaterialModelUvOverrideMap GetModelUvOverrides(const MaterialAssignmentId& materialAssignmentId) const override;
 
+            //! MaterialReceiverNotificationBus::Handler overrides...
+            void OnMaterialAssignmentsChanged() override;
+
         private:
 
             AZ_DISABLE_COPY(MaterialComponentController);