message: Add get transfer manager
diff: @@ -181,6 +181,25 @@ static void GetExecutor(tf_s3_filesystem::S3File* s3_file) {
  }
  }
  +static void GetTransferManager(
  + const Aws::Transfer::TransferDirection& direction,
  + tf_s3_filesystem::S3File* s3_file) {
  + absl::MutexLock l(&s3_file->initialization_lock);
  +
  + if (s3_file->transfer_managers[direction].get() == nullptr) {
  + GetS3Client(s3_file);
  + GetExecutor(s3_file);
  + Aws::Transfer::TransferManagerConfiguration config(s3_file->executor.get());
  + config.s3Client = s3_file->s3_client;
  + config.bufferSize = s3_file->multi_part_chunk_sizes[direction];
  + // must be larger than pool size * multi part chunk size
  + config.transferBufferMaxHeapSize =
  + (kExecutorPoolSize + 1) * s3_file->multi_part_chunk_sizes[direction];
  + s3_file->transfer_managers[direction] =
  + Aws::Transfer::TransferManager::Create(config);
  + }
  +}
  +
  static void ShutdownClient(Aws::S3::S3Client* s3_client) {
  if (s3_client != nullptr) {
  delete s3_client;
  