Use the actual Country type instead of the name.

We want other pieces of country information (in particular the short
names). This cleans up a lot of code anyway.

As an added bonus, this now catches squadrons that used invalid names
which would previously be passed through to pydcs and... then I don't
know what would happen.

game/commander/packagefulfiller.py

@@ -143,7 +143,6 @@ class PackageFulfiller:
             self.air_wing,
             self.flight_db,
             self.is_player,
-            self.coalition.country_name,
             self.default_start_type,
             mission.asap,
         )