Reset game state on new turn.

This may not be the way to do this long term, but it is how the old map
works so it's at least not a regression. It might be better to generate
events for the between-turn changes in state instead.

https://github.com/dcs-liberation/dcs_liberation/issues/2039

game/game.py

@@ -307,6 +307,7 @@ class Game:
         with logged_duration("Turn initialization"):
             self.initialize_turn(events)
 
+        events.begin_new_turn()
         EventStream.put_nowait(events)
 
         # Autosave progress