Switch analysis_server to use 'package:test'.

pkg/analysis_server/test/plugin/test_all.dart

Index: pkg/analysis_server/test/plugin/test_all.dart
diff --git a/pkg/analysis_server/test/plugin/test_all.dart b/pkg/analysis_server/test/plugin/test_all.dart
index 5ad008b5e2367ff3e1d718876e7241eced558be2..7c0e5aaa81eda389aa579f53fd8160714f388589 100644
--- a/pkg/analysis_server/test/plugin/test_all.dart
+++ b/pkg/analysis_server/test/plugin/test_all.dart
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 library test.plugin.analysis_contributor;
 
-import 'package:unittest/unittest.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../utils.dart';
 import 'protocol_dart_test.dart' as protocol_dart_test;
@@ -14,8 +14,8 @@ import 'set_analysis_domain_test.dart' as set_analysis_domain_test;
  */
 main() {
   initializeTestEnvironment();
-  group('plugin', () {
+  defineReflectiveSuite(() {
     protocol_dart_test.main();
     set_analysis_domain_test.main();
-  });
+  }, name: 'plugin');
 }