Rewrite test language/constructor_negative_test to a multi-test

tests/language/constructor_negative_test.dart

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-// Dart test program to make sure we catch missing new or const
-// when allocating a new object.
-
-
-class Point {
-  const Point(this.x, this.y);
-  final int x;
-  final int y;
-}
-
-
-class ConstructorNegativeTest {
-  static testMain() {
-    Point p = Point(1, 2);   // should be const or new before Point(1,2).
-  }
-}
-
-main() {
-  ConstructorNegativeTest.testMain();
-}