Method DeliverBatches

cpp/src/arrow/dataset/scanner_test.cc:202–211

### Unit Test API ###

  // ### Unit Test API ###
  void DeliverBatches(bool slow, const std::vector<MockScanTask>& to_deliver) {
    for (MockScanTask task : to_deliver) {
      if (slow) {
        std::ignore = SleepABitAsync().Then(
            [task]() mutable { task.batch_future.MarkFinished(task.batch); });
      } else {
        task.batch_future.MarkFinished(task.batch);
      }
    }
  }

  void DeliverBatchesInOrder(bool slow) { DeliverBatches(slow, scan_tasks_); }