[Serverless] Disable Advanced settings plugin (#159819)

Partially addresses https://github.com/elastic/kibana/issues/159590

## Summary

This PR disables the Advanced settings plugin for all projects in
serverless.

**How to test:**

1. Start Elasticsearch with `yarn es snapshot` and Kibana with `yarn
serverless-{mode}` where {mode} can be `es`, `security`, or `oblt`.
2. Verify that the Advanced settings app is not accessible and its
endpoint (`app/management/kibana/settings`) leads to the Stack
Management landing page.

---------

Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>

config/serverless.yml

@@ -23,6 +23,7 @@ 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

@@ -0,0 +1,20 @@
+/*
+ * 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

@@ -9,5 +9,7 @@
 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

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