refactor: add Metadata.hasViewTagAtIndex() method.

Author: endel

src/Metadata.ts

@@ -285,5 +285,9 @@ export const Metadata = {
             fields[metadata[i].name] = metadata[i].type;
         }
         return fields;
+    },
+
+    hasViewTagAtIndex(metadata: Metadata, index: number) {
+        return metadata?.[$viewFieldIndexes]?.includes(index);
     }
 }

src/encoder/ChangeTree.ts

@@ -571,7 +571,7 @@ export class ChangeTree<T extends Ref=any> {
         }
         key += `-${parentIndex}`;
 
-        const fieldHasViewTag = parentConstructor?.[Symbol.metadata]?.[$viewFieldIndexes]?.includes(parentIndex);
+        const fieldHasViewTag = Metadata.hasViewTagAtIndex(parentConstructor?.[Symbol.metadata], parentIndex);
 
         this.isFiltered = parent[$changes].isFiltered // in case parent is already filtered
             || this.root.types.parentFiltered[key]