stream_settings: Add 'Default stream' option in edit stream UI.

This commit adds a 'Default stream for new users' checkbox in
the stream editing UI to allow admins to easily add or remove
a stream as the default stream for new users. Previously, this
functionality required navigating to separate menu.

Fixes a part of #24048.

web/src/server_events_dispatch.js

@@ -102,6 +102,7 @@ export function dispatch_normal_event(event) {
         case "default_streams":
             stream_data.set_realm_default_streams(event.default_streams);
             settings_streams.update_default_streams_table();
+            stream_settings_ui.update_is_default_stream();
             break;
 
         case "delete_message": {