message: [expr] more informative message for degree error
diff: @@ -1280,7 +1280,7 @@ impl<F: FftField> Expr<F> {
  } else if deg <= 8 * d1_size {
  Domain::D8
  } else {
  - panic!("constraint had degree {} > 8", deg);
  + panic!("constraint had degree {deg} > d8 ({})", 8 * d1_size);
  };
  let mut cache = HashMap::new();
  