move performance measurement to benchmark/integration

pkg/analysis_server/benchmark/integration/main.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 server.performance;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
@@ skipping 220 matching lines @@
   /**
    * The temporary directory containing source used during performance measurement.
    */
   String tmpSrcDirPath;
 
   /**
    * The diagnostic port for Analysis Server or `null` if none.
    */
   int diagnosticPort;
 }