feat(io): Add position property to InterfaceDevice

Introduced a new `position` property with read access in the D-Bus
interface and implemented its corresponding method.

Signed-off-by: Sven Sager <s.sager@kunbus.com>

src/revpi_middleware/ios1/interface_devices.py

@@ -59,6 +59,7 @@ class InterfaceDevice:
             <property name="inp" type="ao" access="read"/>
             <property name="name" type="s" access="read"/>
             <property name="out" type="ao" access="read"/>
+            <property name="position" type="n" access="read"/>
             <property name="type" type="s" access="read"/>
         </interface>
     </node>
@@ -99,6 +100,10 @@ class InterfaceDevice:
     def out(self) -> list[str]:
         return [get_io_object_path(io) for io in self.device.get_outputs()]
 
+    @property
+    def position(self) -> int:
+        return self.device.position
+
     @property
     def type(self):
         return self.device.type