Remove old index and search implementations.

pkg/analysis_server/test/services/index/store/single_source_container.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 test.services.src.index.store.single_source_container;
-
-import 'package:analyzer/src/generated/source.dart';
-
-/**
- * A [SourceContainer] with a single [Source].
- */
-class SingleSourceContainer implements SourceContainer {
-  final Source _source;
-
-  SingleSourceContainer(this._source);
-
-  @override
-  bool contains(Source source) => source == _source;
-}