message: [logging] Add thread name to text log output
  Closes:
diff: @@ -336,18 +336,23 @@ impl Writer for FileWriter {
  }
  /// Converts a record into a string representation:
  -/// UNIX_TIMESTAMP LOG_LEVEL FILE:LINE MESSAGE
  +/// UNIX_TIMESTAMP LOG_LEVEL [thread_name] FILE:LINE MESSAGE JSON_DATA
  /// Example:
  -/// 2020-03-07 05:03:03 INFO common/libra-logger/src/lib.rs:261 Hello
  +/// 2020-03-07 05:03:03 INFO [thread_name] common/libra-logger/src/lib.rs:261 Hello { "world": true }
  fn format(entry: &LogEntry) -> Result<String, fmt::Error> {
  use std::fmt::Write;
  let mut w = String::new();
  + write!(w, "{}", entry.timestamp)?;
  +
  + if let Some(thread_name) = &entry.thread_name {
  + write!(w, " [{}]", thread_name)?;
  + }
  +
  write!(
  w,
  - "{} {} {}",
  + " {} {}",
  entry.metadata.level(),
  - entry.timestamp,
  entry.metadata.location()
  )?;
  