Rationalize Dart mojo and sky package structure

mojo/public/dart/lib/src/types.dart

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 part of core;
 
 class MojoResult {
   static const int kOk = 0;
   static const int kCancelled = 1;
   static const int kUnknown = 2;
@@ skipping 240 matching lines @@
   final MojoResult result;
   final int index;
   List<MojoHandleSignalsState> states;
 
   bool get isIndexValid => (this.index != null);
   bool get areSignalStatesValid => (this.states != null);
 
   String toString() =>
       "MojoWaitManyResult(" "result: $result, idx: $index, state: ${states[index]})";
 }