Revert "[Serverless] Disable Advanced settings plugin (#159819)" (#160404)

This reverts commit ca425e8993.

## Summary

Reverts the changes from https://github.com/elastic/kibana/pull/159819
in 8.9 since it was intended to go into 8.10 but it was accidentally
merged into 8.9.

config/serverless.yml

@@ -23,7 +23,6 @@ xpack.license_management.enabled: false
 xpack.reporting.enabled: false
 xpack.cloud_integrations.data_migration.enabled: false
 data.search.sessions.enabled: false
-advanced_settings.enabled: false
 
 # Enforce restring access to internal APIs see https://github.com/elastic/kibana/issues/151940
 # server.restrictInternalApis: true

src/plugins/advanced_settings/server/config.ts

@@ -1,20 +0,0 @@
-/*
- * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
- * or more contributor license agreements. Licensed under the Elastic License
- * 2.0 and the Server Side Public License, v 1; you may not use this file except
- * in compliance with, at your election, the Elastic License 2.0 or the Server
- * Side Public License, v 1.
- */
-
-import { schema, TypeOf } from '@kbn/config-schema';
-import { PluginConfigDescriptor } from '@kbn/core-plugins-server';
-
-const configSchema = schema.object({
-  enabled: schema.boolean({ defaultValue: true }),
-});
-
-export type AdvancedSettingsConfig = TypeOf<typeof configSchema>;
-
-export const config: PluginConfigDescriptor<AdvancedSettingsConfig> = {
-  schema: configSchema,
-};

src/plugins/advanced_settings/server/index.ts

@@ -9,7 +9,5 @@
 import { PluginInitializerContext } from '@kbn/core/server';
 import { AdvancedSettingsServerPlugin } from './plugin';
 
-export { config } from './config';
-
 export const plugin = (initContext: PluginInitializerContext) =>
   new AdvancedSettingsServerPlugin(initContext);

src/plugins/advanced_settings/tsconfig.json

@@ -28,8 +28,6 @@
     "@kbn/core-notifications-browser",
     "@kbn/core-theme-browser",
     "@kbn/core-ui-settings-common",
-    "@kbn/config-schema",
-    "@kbn/core-plugins-server",
   ],
   "exclude": [
     "target/**/*",