Replace CP integer ID with a UUID.

This allows unique identification across saves. The front-end needs to
be able to differentiate the first carrier in game A and the first
carrier in game B, but because carriers (and other non-airfield CPs) are
assigned IDs sequentially, collisions were to be expected. The front-end
can't tell the difference between a reloaded game and a new turn, so we
need to ensure different IDs across games.

This is a handy cleanup anyway, since callers constructing CPs no longer
need to manually track the CP ID counter.

Fixes https://github.com/dcs-liberation/dcs_liberation/issues/2078.

qt_ui/windows/basemenu/QBaseMenu2.py

@@ -39,12 +39,6 @@ class QBaseMenu2(QDialog):
         self.game_model = game_model
         self.objectName = "menuDialogue"
 
-        try:
-            game = self.game_model.game
-            self.airport = game.theater.terrain.airport_by_id(self.cp.id)
-        except:
-            self.airport = None
-
         if self.cp.captured:
             self.deliveryEvent = None