message: update Iterable abstract base class in bentleyjs-core
diff: * @param list the wrapped array that this class support iteration over
  */
  export abstract class Iterable<T> {
  - constructor(protected list: T[]) { }
  + constructor(protected _list: T[] = []) { }
  public [Symbol.iterator]() {
  let key = 0;
  - return { next: (): IteratorResult<T> => { const result = key < this.list.length ? { value: this.list[key], done: false } : { value: this.list[key - 1], done: true }; key++; return result; } };
  + return { next: (): IteratorResult<T> => { const result = key < this._list.length ? { value: this._list[key], done: false } : { value: this._list[key - 1], done: true }; key++; return result; } };
  }
  }
  