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

pkg/analyzer/test/source/test_all.dart

Index: pkg/analyzer/test/source/test_all.dart
diff --git a/pkg/analyzer/test/source/test_all.dart b/pkg/analyzer/test/source/test_all.dart
index d2de4334fd20440fe29b48df122cf0f398cf1e1b..b8c09bf99d3e1b93da3d3164f6b9c4d291862034 100644
--- a/pkg/analyzer/test/source/test_all.dart
+++ b/pkg/analyzer/test/source/test_all.dart
@@ -8,6 +8,7 @@ import 'package:unittest/unittest.dart';
 
 import 'package_map_provider_test.dart' as package_map_provider_test;
 import 'package_map_resolver_test.dart' as package_map_resolver_test;
+import 'sdk_ext_test.dart' as sdk_ext_test;
 
 /// Utility for manually running all tests.
 main() {
@@ -15,5 +16,6 @@ main() {
   group('source', () {
     package_map_provider_test.main();
     package_map_resolver_test.main();
+    sdk_ext_test.main();
   });
 }