message: nydusctl: beautify backend metrics display
  Make it more human readable
diff: @@ -211,15 +211,24 @@ Read Errors: {read_errors}
  println!(
  r#"
  -Block Sizes/millis:
  -{:<8}{:<8}{:<8}{:<8}{:<8}{:<8}{:<8}{:<8}"#,
  - sizes[0], sizes[1], sizes[2], sizes[3], sizes[4], sizes[5], sizes[6], sizes[7]
  +{:<25}{:<8}{:<8}{:<8}{:<8}{:<8}{:<8}{:<8}{:<8}"#,
  + "Block Sizes:",
  + sizes[0],
  + sizes[1],
  + sizes[2],
  + sizes[3],
  + sizes[4],
  + sizes[5],
  + sizes[6],
  + sizes[7],
  );
  let latency_cumulative_dist =
  m["read_cumulative_latency_millis_dist"].as_array().unwrap();
  let latency_block_hits = m["read_count_block_size_dist"].as_array().unwrap();
  + print!("{:<25}", "Average Latency(millis):");
  +
  for (i, _) in sizes.iter().enumerate() {
  print!(
  "{:<8}",
  @@ -235,11 +244,20 @@ Block Sizes/millis:
  println!(
  r#"
  -Block Sizes:
  -{:<8}{:<8}{:<8}{:<8}{:<8}{:<8}{:<8}{:<8}"#,
  - sizes[0], sizes[1], sizes[2], sizes[3], sizes[4], sizes[5], sizes[6], sizes[7]
  +{:<25}{:<8}{:<8}{:<8}{:<8}{:<8}{:<8}{:<8}{:<8}"#,
  + "Block Sizes:",
  + sizes[0],
  + sizes[1],
  + sizes[2],
  + sizes[3],
  + sizes[4],
  + sizes[5],
  + sizes[6],
  + sizes[7]
  );
  + print!("{:<25}", "Request Count:");
  +
  for (i, _) in sizes.iter().enumerate() {
  print!("{:<8}", latency_block_hits[i].as_u64().unwrap());
  }
  