Restructure the public API for server

pkg/analysis_server/lib/plugin/index/index_core.dart

Index: pkg/analysis_server/lib/plugin/index/index_core.dart
diff --git a/pkg/analysis_server/lib/analysis/index_core.dart b/pkg/analysis_server/lib/plugin/index/index_core.dart
similarity index 99%
rename from pkg/analysis_server/lib/analysis/index_core.dart
rename to pkg/analysis_server/lib/plugin/index/index_core.dart
index 58e996ed6590bf10fd56e5c9fcc3c13b614fe8c2..98fde3eff0d966162dd8c00153fa2570e927e2b1 100644
--- a/pkg/analysis_server/lib/analysis/index_core.dart
+++ b/pkg/analysis_server/lib/plugin/index/index_core.dart
@@ -2,7 +2,7 @@
 // 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.analysis.index.index_core;
+library analysis_server.plugin.index.index_core;
 
 import 'dart:async';
 import 'dart:collection';