Deprecate the generated AST library and clean up imports

pkg/analysis_server/lib/src/domains/analysis/navigation_dart.dart

 // Copyright (c) 2015, 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 domains.analysis.navigation_dart;
 
 import 'package:analysis_server/plugin/analysis/navigation/navigation_core.dart';
 import 'package:analysis_server/src/protocol_server.dart' as protocol;
+import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
+import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/src/dart/ast/utilities.dart';
 import 'package:analyzer/src/dart/element/element.dart';
-import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 
 /**
  * A computer for navigation regions in a Dart [CompilationUnit].
  */
 class DartNavigationComputer implements NavigationContributor {
   @override
   void computeNavigation(NavigationCollector collector, AnalysisContext context,
       Source source, int offset, int length) {
@@ skipping 299 matching lines @@
       }
     }
   }
 
   void _safelyVisit(AstNode node) {
     if (node != null) {
       node.accept(this);
     }
   }
 }