Rename package_root.dart test to package_root_test.dart

pkg/analysis_server/test/integration/analysis/package_root_test.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.integration.analysis.packageRoot;
 
 import 'package:analysis_server/src/protocol.dart';
 import 'package:path/path.dart';
 import 'package:unittest/unittest.dart';
 
@@ skipping 47 matching lines @@
         }
       }
       expect(found, isTrue);
     });
   }
 }
 
 main() {
   runReflectiveTests(Test);
 }