message: Improve Debug formatting of the thread name.
diff: @@ -132,13 +132,9 @@ impl<'mir, 'tcx> Thread<'mir, 'tcx> {
  impl<'mir, 'tcx> std::fmt::Debug for Thread<'mir, 'tcx> {
  fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
  if let Some(ref name) = self.thread_name {
  - if let Ok(name_str) = std::str::from_utf8(name) {
  - write!(f, "{}", name_str)?;
  + write!(f, "{}", String::from_utf8_lossy(name))?;
  } else {
  - write!(f, "<invalid thread name>")?;
  - }
  - } else {
  - write!(f, "unnamed")?;
  + write!(f, "<unnamed>")?;
  }
  write!(f, "({:?}, {:?})", self.state, self.join_status)
  }
  