Move the wire protocol support into the public API

pkg/analysis_server/test/search/top_level_declarations_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.search.top_level_declarations;
 
 import 'dart:async';
 
-import 'package:analysis_server/src/protocol.dart';
+import 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 import 'package:unittest/unittest.dart';
 
 import '../utils.dart';
 import 'abstract_search_domain.dart';
 
 main() {
   initializeTestEnvironment();
   defineReflectiveTests(TopLevelDeclarationsTest);
 }
@@ skipping 45 matching lines @@
 ''');
     await findTopLevelDeclarations('^[A-E]\$');
     assertHasDeclaration(ElementKind.CLASS, 'A');
     assertHasDeclaration(ElementKind.CLASS, 'B');
     assertHasDeclaration(ElementKind.FUNCTION_TYPE_ALIAS, 'C');
     assertHasDeclaration(ElementKind.FUNCTION, 'D');
     assertHasDeclaration(ElementKind.TOP_LEVEL_VARIABLE, 'E');
     assertNoDeclaration(ElementKind.CLASS, 'ABC');
   }
 }