ps: Allow showing compositor info
ps: Allow showing compositor info

Show active and background state, based on information obtained
from the background portal backend about which apps have (active) windows.

This currently tries all known portal backends in turn. It might
be nicer to have a portal frontend api to query this, or to find
out which backend to talk to.

flatpak/flatpak,flatpak/flatpak,flatpak/flatpak,flatpak/flatpak,flatpak/flatpak