Extract testing utilities into a separate package.

pkg/analyzer/test/index/store/codec_test.dart

Index: pkg/analyzer/test/index/store/codec_test.dart
diff --git a/pkg/analyzer/test/index/store/codec_test.dart b/pkg/analyzer/test/index/store/codec_test.dart
index 9bfcbb529c5bf01219439bdfa0087fd0e8db7b17..0d498ad5248b0a9e4de607bfe713d0ad98e86863 100644
--- a/pkg/analyzer/test/index/store/codec_test.dart
+++ b/pkg/analyzer/test/index/store/codec_test.dart
@@ -4,6 +4,8 @@
 
 library test.engine.src.index.store.codec;
 
+import 'package:analysis_testing/mocks.dart';
+import 'package:analysis_testing/reflective_tests.dart';
 import 'package:analyzer/index/index.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/engine.dart';
@@ -11,9 +13,6 @@ import 'package:analyzer/src/index/store/codec.dart';
 import 'package:typed_mock/typed_mock.dart';
 import 'package:unittest/unittest.dart';
 
-import '../../reflective_tests.dart';
-import 'typed_mocks.dart';
-
 
 main() {
   groupSep = ' | ';