Deprecate the generated AST library and clean up imports

pkg/analyzer/test/src/abstract_single_unit.dart

Index: pkg/analyzer/test/src/abstract_single_unit.dart
diff --git a/pkg/analyzer/test/src/abstract_single_unit.dart b/pkg/analyzer/test/src/abstract_single_unit.dart
index 48ba251bc54360398c64edf8a56504c2279907e9..1955d6e17030db5f24be4b0d07486b5d96547dd6 100644
--- a/pkg/analyzer/test/src/abstract_single_unit.dart
+++ b/pkg/analyzer/test/src/abstract_single_unit.dart
@@ -4,8 +4,9 @@
 
 library test.services.src.index.abstract_single_file;
 
+import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
-import 'package:analyzer/src/generated/ast.dart';
+import 'package:analyzer/src/dart/ast/utilities.dart';
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/java_engine.dart';
 import 'package:analyzer/src/generated/source.dart';