Remove the options plugin

pkg/analyzer/lib/plugin/options.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.
 
 /// Support for client code that wants to consume options contributed to the
 /// analysis options file.
 library analyzer.plugin.options;
 
 import 'package:analyzer/error/listener.dart';
-import 'package:analyzer/src/plugin/options_plugin.dart';
-import 'package:plugin/plugin.dart';
 import 'package:yaml/yaml.dart';
 
-/// The identifier of the extension point that allows plugins to validate
-/// options defined in the analysis options file. The object used as an
-/// extension must be an [OptionsValidator].
-final String OPTIONS_VALIDATOR_EXTENSION_POINT_ID = Plugin.join(
-    OptionsPlugin.UNIQUE_IDENTIFIER,
-    OptionsPlugin.OPTIONS_VALIDATOR_EXTENSION_POINT);
-
 /// Validates options as defined in an analysis options file.
 ///
 /// The options file format is intentionally very open-ended, giving clients
 /// utmost flexibility in defining their own options.  The only hardfast
 /// expectation is that options files will contain a mapping from Strings
 /// (identifying 'scopes') to associated options.  For example, the given
 /// content
 ///
 ///     linter:
 ///       rules:
@@ skipping 14 matching lines @@
 ///
 ///     bool useMultiPackage =
 ///         options['compiler']['resolver']['useMultiPackage'];
 ///
 /// Clients may implement this class when implementing plugins.
 ///
 abstract class OptionsValidator {
   /// Validate [options], reporting any errors to the given [reporter].
   void validate(ErrorReporter reporter, Map<String, YamlNode> options);
 }