py/obj: Accept user types in mp_obj_get_int_maybe.

This is possible now that MP_UNARY_OP_INT_MAYBE exists.

As a consequence mp_obj_get_int now also supports user types, which was
previously possible with MP_UNARY_OP_INT but no tests existed for it.

Signed-off-by: Damien George <damien@micropython.org>

py/obj.c

@@ -326,7 +326,12 @@ bool mp_obj_get_int_maybe(mp_const_obj_t arg, mp_int_t *value) {
     } else if (mp_obj_is_exact_type(arg, &mp_type_int)) {
         *value = mp_obj_int_get_checked(arg);
     } else {
-        return false;
+        arg = mp_unary_op(MP_UNARY_OP_INT_MAYBE, (mp_obj_t)arg);
+        if (arg != MP_OBJ_NULL) {
+            *value = mp_obj_int_get_checked(arg);
+        } else {
+            return false;
+        }
     }
     return true;
 }