The Gtk.Switch representing the p2p.Device's Enabled property should use
the "delayed state change" logic as described in Gtk.Switch docs, i.e.
we need to use .set_state() instead of .set_active() when we get
confirmation of the property having changed its value in the
PropertiesChanged handler. The ::active property is automatically
changed by Gtk.Switch on user input.
This way the UI gives visual feedback of when the device enable/disable
op starts and ends (or fails).
Subscribe to InterfacesAdded/Removed/PropertiesChanged signals before
using GetManagedObjects. For some reason when iwd starts after the
client, we consistently get the managed objects list from before Adapter
interfaces are added but we miss the subsequent InterfacesAdded
signals, probably has to do with the GetManagedObjects and the AddMatch
calls all being synchronous.
Secondly call self.populate_devices() on init as it won't be called if
IWD is not on the bus.
Define a bunch of stream parameters each with a getter and an optional
setter. In the right pane of the window show widgets for these
properties, some as just labels and some as editable controls depending
on the type of the property. Parse the EDID data.
