message: Use fmt::DebugStruct in DebugFields so field names aren't quoted
diff: @@ -405,7 +405,11 @@ where
  &'a I: IntoIterator<Item = (&'a str, &'a dyn Value)>,
  {
  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
  - f.debug_map().entries(self.0.into_iter()).finish()
  + self.0.into_iter()
  + .fold(&mut f.debug_struct(""), |s, (name, value)| {
  + s.field(name, &value)
  + })
  + .finish()
  }
  }
  