2 changes to address the review feedback:
1. Aleksei pointed out in this
comment (https://github.com/Alexays/Waybar/pull/2971#issuecomment-1972364896)
that there's no way to tell if a proxy is alive other than trying to
call a method on it. We perform a little dance to check whether or
not power-profiles-daemon is available on the system by calling
properties.GetAll. If something responds, we assume
power-profiles-daemon is installed, it's then safe to draw the
widget and attach the callback to the active profile.
2. We replaced all the synchronous DBus operations by their async
counterparts.
09bb6a055d