reset method
void
reset()
重置所有状态(用于需要重新开始的场景)
Implementation
void reset() {
_emit(UpgraderEventType.log, '重置所有状态');
_cancelToken?.cancel();
_cancelToken = null;
_updateInfo = null;
_savePath = null;
statusNotifier.value = DownloadStatus.none;
progressNotifier.value = 0.0;
}