feat(cli): Add CLI support for RevPi configuration object (revpi-config)

This implements a new command "config" in the CLI to handle RevPi
configuration. It includes parsing and subparser setup for
configuration-related operations. The change improves usability by
extending CLI functionality to manage RevPi configuration objects.

src/revpi_middleware/cli_commands/dbus_helper.py

@@ -17,6 +17,18 @@ class BusType(Enum):
     SYSTEM = "system"
 
 
+def get_properties(
+    property_name: str,
+    interface: str,
+    object_path=REVPI_DBUS_BASE_PATH,
+    bus_type=BusType.SYSTEM,
+):
+    bus = SessionBus() if bus_type is BusType.SESSION else SystemBus()
+    revpi = bus.get(REVPI_DBUS_NAME, object_path)
+    iface = revpi[interface]
+    return getattr(iface, property_name)
+
+
 def simple_call(
     method: str,
     *args,