Improve frozenset debug representation

For `frozenset([1, 2, "str"])` object, it is represented as
`frozenset { [PyObject PyInt { value: 1 }], [PyObject PyInt { value: 2 }],
[PyObject PyStr { value: "str", kind: Ascii, hash: -845154580267954013 }], }`

Author: moreal

vm/src/builtins/set.rs

@@ -66,7 +66,8 @@ impl fmt::Debug for PySet {
 impl fmt::Debug for PyFrozenSet {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         // TODO: implement more detailed, non-recursive Debug formatter
-        f.write_str("frozenset")
+        f.write_str("PyFrozenSet ")?;
+        f.debug_set().entries(self.elements().iter()).finish()
     }
 }