Revert "Move the linter core to the analyzer package"

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

-// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
-// 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.
-
-import 'dart:collection';
-
-import 'package:analyzer/src/lint/config.dart';
-import 'package:analyzer/src/lint/linter.dart';
-
-/**
- * Registry of contributed lint rules.
- */
-class Registry extends Object with IterableMixin<LintRule> {
-  /**
-   * The default registry to be used by clients.
-   */
-  static final Registry ruleRegistry = new Registry();
-
-  Map<String, LintRule> _ruleMap = <String, LintRule>{};
-
-  @override
-  Iterator<LintRule> get iterator => _ruleMap.values.iterator;
-
-  Iterable<LintRule> get rules => _ruleMap.values;
-
-  LintRule operator [](String key) => _ruleMap[key];
-
-  /// All lint rules explicitly enabled by the given [config].
-  ///
-  /// For example:
-  ///     my_rule: true
-  ///
-  /// enables `my_rule`.
-  ///
-  /// Unspecified rules are treated as disabled by default.
-  Iterable<LintRule> enabled(LintConfig config) => rules
-      .where((rule) => config.ruleConfigs.any((rc) => rc.enables(rule.name)));
-
-  void register(LintRule rule) {
-    _ruleMap[rule.name] = rule;
-  }
-}