This allows the applet to be restarted on panel configuration changes
without replacing the daemon, or having races between different applet
instances trying to run the watcher.
Otherwise, this should behave similarly to the existing version.
Should fix https://github.com/pop-os/cosmic-panel/issues/284.
Fixes issue where `fcitx5` app icon persists after it is no longer
running. It seems it was getting a `NameOwnerChanged` event with the
acquired name after `register_status_notifier_item()`.
This is based on the GTK version of the status area applet that was
previously in this repository.
This exposes app indicators found over dbus. As used in applications
like nm-applet and steam.
