Add option to limit squadron sizes and begin full.

Adding temporarily as an option to make sure it's not a terrible idea,
but the old mode will probably go away.

Fixes https://github.com/dcs-liberation/dcs_liberation/issues/1583.
Fixes https://github.com/dcs-liberation/dcs_liberation/issues/2808.

game/procurement.py

@@ -234,6 +234,8 @@ class ProcurementAi:
         ):
             if not squadron.can_provide_pilots(request.number):
                 continue
+            if not squadron.has_aircraft_capacity_for(request.number):
+                continue
             if squadron.location.unclaimed_parking() < request.number:
                 continue
             if self.threat_zones.threatened(squadron.location.position):