Move scanner out of generated and clean up imports

pkg/analyzer/test/dart/ast/ast_test.dart

 // Copyright (c) 2014, 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.
 
 library analyzer.test.dart.ast.ast_test;
 
 import 'package:analyzer/dart/ast/ast.dart';
-import 'package:analyzer/src/generated/scanner.dart';
+import 'package:analyzer/dart/ast/token.dart';
+import 'package:analyzer/src/dart/ast/token.dart';
 import 'package:analyzer/src/generated/testing/ast_factory.dart';
 import 'package:analyzer/src/generated/testing/token_factory.dart';
 import 'package:unittest/unittest.dart';
 
 import '../../generated/parser_test.dart' show ParserTestCase;
 import '../../generated/test_support.dart';
 import '../../reflective_tests.dart';
 import '../../utils.dart';
 
 main() {
@@ skipping 1279 matching lines @@
   final int ordinal;
 
   const _WrapperKind(this.name, this.ordinal);
 
   int get hashCode => ordinal;
 
   int compareTo(_WrapperKind other) => ordinal - other.ordinal;
 
   String toString() => name;
 }