message: nydusctl: print each prefetch item to new line
diff: @@ -416,13 +416,13 @@ Commit: {git_commit}
  let cfg = backend.config.unwrap();
  let cache_cfg = cfg.get_cache_config()?;
  let rafs_cfg = cfg.get_rafs_config()?;
  - print!("\tMode: {}", rafs_cfg.mode);
  - print!("\tPrefetch: {}", cache_cfg.prefetch.enable);
  - print!(
  + println!("\tMode: {}", rafs_cfg.mode);
  + println!("\tPrefetch: {}", cache_cfg.prefetch.enable);
  + println!(
  "\tPrefetch Merging Size: {}",
  cache_cfg.prefetch.batch_size
  );
  - print!("")
  + println!();
  }
  }
  }
  