dispose method

Implementation

@mustCallSuper
void dispose() {
  // TODO(polina-c): stop duplicating code across disposables
  // https://github.com/flutter/flutter/issues/137435
  if (kFlutterMemoryAllocationsEnabled) {
    FlutterMemoryAllocations.instance.dispatchObjectDisposed(object: this);
  }

  for (final _HeroFlight flight in _flights.values) {
    flight.dispose();
  }
}