8261 - Avoid including Cesium3DTileFeature, fix imports

Author: Samuel Vargas

Source/Scene/Cesium3DTileFeature.js

@@ -41,6 +41,15 @@ import defineProperties from '../Core/defineProperties.js';
         this._content = content;
         this._batchId = batchId;
         this._color = undefined;  // for calling getColor
+
+        /**
+         * NOTE: This property exists so that `Picking.js` can differentiate between
+         *       PrimitiveCollections and isCesium3DTileFeature objects without inflating
+         *       the size of the module via `instance of Cesium3DTileFeature`
+         * @private
+         */
+
+        this.isCesium3DTileFeature = true;
     }
 
     defineProperties(Cesium3DTileFeature.prototype, {

Source/Scene/Picking.js

@@ -17,10 +17,8 @@ import  Ray from '../Core/Ray.js';
 import  ShowGeometryInstanceAttribute from '../Core/ShowGeometryInstanceAttribute.js';
 import  when from '../ThirdParty/when.js';
 import  Camera from './Camera.js';
-import  Cesium3DTileFeature from './Cesium3DTileFeature.js';
 import  Cesium3DTilePass from './Cesium3DTilePass.js';
 import  Cesium3DTilePassState from './Cesium3DTilePassState.js';
-import  Cesium3DTileset from './Cesium3DTileset.js';
 import  PickDepth from './PickDepth.js';
 import  PrimitiveCollection from './PrimitiveCollection.js';
 import  SceneMode from './SceneMode.js';
@@ -421,7 +419,7 @@ import  View from './View.js';
                 }
             }
 
-            if (object instanceof Cesium3DTileFeature) {
+            if (defined(object.isCesium3DTileFeature)) {
                 hasShowAttribute = true;
                 object.show = false;
                 pickedFeatures.push(object);