Move SdkExtUriResolver from analysis_server to analyzer so it can be used in analyzer_cli

pkg/analyzer/test/source/sdk_ext_test.dart

Index: pkg/analyzer/test/source/sdk_ext_test.dart
diff --git a/pkg/analysis_server/test/src/sdk_ext_test.dart b/pkg/analyzer/test/source/sdk_ext_test.dart
similarity index 97%
rename from pkg/analysis_server/test/src/sdk_ext_test.dart
rename to pkg/analyzer/test/source/sdk_ext_test.dart
index f07417821e96231bd85aaeda3520c0c574462801..b6262193325d2c8e5517a24502b8363382776c92 100644
--- a/pkg/analysis_server/test/src/sdk_ext_test.dart
+++ b/pkg/analyzer/test/source/sdk_ext_test.dart
@@ -2,11 +2,11 @@
 // 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 analysis_server.test.src.sdk_ext;
+library test.source.sdk_ext;
 
-import 'package:analysis_server/src/sdk_ext.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
+import 'package:analyzer/source/sdk_ext.dart';
 import 'package:unittest/unittest.dart';
 
 MemoryResourceProvider resourceProvider;