Clean up imports in analysis_server and analyzer_cli (and one missed in analyzer)

pkg/analysis_server/lib/src/computer/computer_overrides.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 computer.overrides;
 
 import 'package:analysis_server/src/collections.dart';
 import 'package:analysis_server/src/protocol_server.dart';
+import 'package:analyzer/dart/element/element.dart' as engine;
+import 'package:analyzer/dart/element/type.dart' as engine;
 import 'package:analyzer/src/generated/ast.dart';
-import 'package:analyzer/src/generated/element.dart' as engine;
 
 /**
  * A computer for class member overrides in a Dart [CompilationUnit].
  */
 class DartUnitOverridesComputer {
   static const List<ElementKind> FIELD_KINDS = const <ElementKind>[
     ElementKind.FIELD,
     ElementKind.GETTER,
     ElementKind.SETTER
   ];
@@ skipping 145 matching lines @@
     if (kinds.contains(ElementKind.SETTER)) {
       member = classElement.lookUpSetter(name + '=', library);
       if (member != null) {
         return member;
       }
     }
     // not found
     return null;
   }
 }