Move completion APIs to a private location

pkg/analysis_server/test/services/completion/completion_computer_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.services.completion.suggestion;
 
 import 'dart:async';
 
-import 'package:analysis_server/completion/completion_core.dart'
-    show CompletionRequest, CompletionResult;
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/protocol.dart';
+import 'package:analysis_server/src/provisional/completion/completion_core.dart'
+    show CompletionRequest, CompletionResult;
 import 'package:analysis_server/src/services/completion/completion_manager.dart';
 import 'package:analysis_server/src/services/completion/dart_completion_manager.dart';
 import 'package:analysis_server/src/services/index/index.dart';
 import 'package:analysis_server/src/services/index/local_memory_index.dart';
 import 'package:analysis_server/src/services/search/search_engine.dart';
 import 'package:analysis_server/src/services/search/search_engine_internal.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 import 'package:unittest/unittest.dart';
@@ skipping 175 matching lines @@
   @override
   Future<bool> computeFull(DartCompletionRequest request) {
     this.request = request;
     fullCount++;
     if (fullSuggestion != null) {
       request.addSuggestion(fullSuggestion);
     }
     return new Future.value(fullSuggestion != null);
   }
 }