fix(AbstractWidgetFactory): Fix view widget model

Widgets should not take on the WidgetFactory's model. Instead,
explicitly specify what members we want from the factory object.

This avoids populating widgetModel.classHierarchy with unnecessary classes.

Sources/Widgets/Core/AbstractWidgetFactory/index.js

@@ -31,10 +31,15 @@ function vtkAbstractWidgetFactory(publicAPI, model) {
         camera,
       } = extractRenderingComponents(renderer);
       const widgetModel = {};
-      const widgetPublicAPI = {
+      const widgetPublicAPI = {};
+
+      macro.obj(widgetPublicAPI, widgetModel);
+      Object.assign(widgetPublicAPI, {
         onWidgetChange: publicAPI.onWidgetChange,
-      };
-      Object.assign(widgetModel, model, {
+      });
+      Object.assign(widgetModel, {
+        widgetState: model.widgetState,
+        manipulator: model.manipulator,
         viewType,
         renderer,
         camera,