js: Port dbusUtils to ESM

The module is shared between the various D-Bus services and the
main gnome-shell process, so it was originally left out to allow
porting different bits at their own speed.

Now that everything has been ported to ESM, there is no reason
to not move that particular module as well.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2868>

js/ui/status/backgroundApps.js

@@ -11,7 +11,7 @@ import * as Util from '../../misc/util.js';
 
 import {Spinner} from '../animation.js';
 import {QuickToggle, SystemIndicator} from '../quickSettings.js';
-const {loadInterfaceXML} = imports.misc.dbusUtils;
+import {loadInterfaceXML} from '../../misc/dbusUtils.js';
 
 const DBUS_NAME = 'org.freedesktop.background.Monitor';
 const DBUS_OBJECT_PATH = '/org/freedesktop/background/monitor';