analyzer: Use less analyzer private API in linter code

Change-Id: I674c81a19caa5facaf7c7f1217fc8624b21dfa2f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/427840
Commit-Queue: Konstantin Shcheglov <[email protected]>
Auto-Submit: Samuel Rawlins <[email protected]>
Commit-Queue: Samuel Rawlins <[email protected]>
Reviewed-by: Konstantin Shcheglov <[email protected]>

Author: srawlins

pkg/analyzer/lib/src/lint/linter.dart

@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:analyzer/dart/analysis/results.dart';
+import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type_provider.dart';
@@ -11,7 +12,6 @@ import 'package:analyzer/diagnostic/diagnostic.dart';
 import 'package:analyzer/error/error.dart';
 import 'package:analyzer/error/listener.dart';
 import 'package:analyzer/file_system/file_system.dart';
-import 'package:analyzer/src/dart/ast/ast.dart';
 import 'package:analyzer/src/dart/element/inheritance_manager3.dart';
 import 'package:analyzer/src/lint/linter_visitor.dart' show NodeLintRegistry;
 import 'package:analyzer/src/lint/pub.dart';