Deprecate the generated AST library and clean up imports

pkg/analysis_server/lib/src/provisional/completion/dart/completion_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 analysis_server.src.provisional.completion.completion_dart;
 
 import 'dart:async';
 
 import 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:analysis_server/src/provisional/completion/completion_core.dart';
 import 'package:analysis_server/src/provisional/completion/dart/completion_target.dart';
+import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
-import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/source.dart';
 
 export 'package:analysis_server/src/provisional/completion/completion_core.dart'
     show EMPTY_LIST;
 
 const int DART_RELEVANCE_COMMON_USAGE = 1200;
 const int DART_RELEVANCE_DEFAULT = 1000;
 const int DART_RELEVANCE_HIGH = 2000;
 const int DART_RELEVANCE_INHERITED_ACCESSOR = 1057;
 const int DART_RELEVANCE_INHERITED_FIELD = 1058;
@@ skipping 104 matching lines @@
   /**
    * Return a [Future] that completes with a list of [CompilationUnitElement]s
    * comprising the library in which in which the completion is occurring.
    * The [Future] may return `null` if the library unit cannot be determined
    * (e.g. unlinked part file).
    * Any information obtained from [target] prior to calling this method
    * should be discarded as it may have changed.
    */
   Future<List<CompilationUnitElement>> resolveUnits();
 }