Handle runway damage in the debrief.

Apparently we were already getting this info because it's a unit like
any other according to the event system, so if runways were actually
sufficiently damaged we'd emit a ton of exceptions.

This doesn't do anything yet, but tracks the damage state. Will add the
ability to repair them next, and then finally make the damage render the
runway inoperable.

game/operation/operation.py

@@ -32,6 +32,7 @@ from gen.triggergen import TRIGGER_RADIUS_MEDIUM, TriggersGenerator
 
 from .. import db
 from ..debriefing import Debriefing
+from ..theater import Airfield
 from ..unitmap import UnitMap
 
 if TYPE_CHECKING:
@@ -173,6 +174,9 @@ class Operation:
     @classmethod
     def create_unit_map(cls) -> None:
         cls.unit_map = UnitMap()
+        for control_point in cls.game.theater.controlpoints:
+            if isinstance(control_point, Airfield):
+                cls.unit_map.add_airfield(control_point)
 
     @classmethod
     def create_radio_registries(cls) -> None: