Migrate first block of tests in standalone to standalone_2

tests/standalone_2/causal_async_stack_test.dart

 // Copyright (c) 2017, 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.
 // VMOptions=--causal_async_stacks
 
 import "package:expect/expect.dart";
 
 baz() async {
   throw "Bad!";
 }
 
 bar() async {
   await baz();
 }
 
 foo() async {
   await bar();
 }
 
 main() async {
   try {
     await foo();
   } catch (e, st) {
     Expect.isTrue(st.toString().contains("baz"));
     Expect.isTrue(st.toString().contains("bar"));
     Expect.isTrue(st.toString().contains("foo"));
     Expect.isTrue(st.toString().contains("main"));
   }
 }