Use Python dbus-next D-Bus library (#3234)

* Use the correct interface name to get properties of systemd

It seems that gdbus (or systemd) automatically pick the correct
interface and return the properties. However, dbussy requires the
correct interface name to get all properties.

* Don't expect array from Strength property

The property returns a type "y" which equates to "guchar":
https://developer-old.gnome.org/NetworkManager/stable/gdbus-org.freedesktop.NetworkManager.AccessPoint.html#gdbus-property-org-freedesktop-NetworkManager-AccessPoint.Strength

It seems that the old D-Bus implementation returned an array. With
dbus-next a integer is returned, so no list indexing required.

* Support signals and remove no longer used tests and code

* Pass rauc update file path as string

That is what the interface is expecting, otherwise the new lib chocks on
the Pathlib type.

* Support Network configuration with dbus-next

Assemble Python native objects and pass them to dbus-next. Use dbus-next
specific Variant class where necessary.

* Use org.freedesktop.NetworkManager.Connection.Active.StateChanged

org.freedesktop.NetworkManager.Connection.Active.PropertyChanged is
depricated. Also it seems that StateChanged leads to fewer and more
accurate signals.

* Pass correct data type to RequestScan.

RequestScan expects an option dictionary. Pass an empty option
dictionary to it.

* Update unit tests

Replace gdbus specific fixtures with json files representing the return
values. Those can be easily converted into native Python objects.

* Rename D-Bus utils module gdbus to dbus

supervisor/exceptions.py

@@ -263,35 +263,31 @@ class ServicesError(HassioError):
     """Services Errors."""
 
 
-# utils/gdbus
+# utils/dbus
 
 
 class DBusError(HassioError):
-    """DBus generic error."""
+    """D-Bus generic error."""
 
 
 class DBusNotConnectedError(HostNotSupportedError):
-    """DBus is not connected and call a method."""
+    """D-Bus is not connected and call a method."""
 
 
 class DBusInterfaceError(HassioNotSupportedError):
-    """DBus interface not connected."""
+    """D-Bus interface not connected."""
 
 
 class DBusFatalError(DBusError):
-    """DBus call going wrong."""
+    """D-Bus call going wrong."""
 
 
 class DBusInterfaceMethodError(DBusInterfaceError):
-    """Dbus method was not definied."""
+    """D-Bus method was not defined."""
 
 
 class DBusParseError(DBusError):
-    """DBus parse error."""
-
-
-class DBusProgramError(DBusError):
-    """DBus application error."""
+    """D-Bus parse error."""
 
 
 # util/apparmor