Change squadrons to operate out of a single base.

https://github.com/dcs-liberation/dcs_liberation/issues/1145

Currently this is fixed at the start of the campaign. The squadron
locations are defined by the campaign file.

Follow up work:

* Track aircraft ownership per-squadron rather than per-airbase.
* UI for relocating squadrons.
* Ferry missions for squadrons that are relocating.
* Auto-relocation (probably only for retreat handling).

Fixes https://github.com/dcs-liberation/dcs_liberation/issues/1138

game/campaignloader/campaign.py

@@ -10,7 +10,6 @@ from typing import Tuple, Dict, Any
 from packaging.version import Version
 import yaml
 
-from game.campaignloader.mizcampaignloader import MizCampaignLoader
 from game.profiling import logged_duration
 from game.theater import (
     ConflictTheater,
@@ -23,6 +22,8 @@ from game.theater import (
     MarianaIslandsTheater,
 )
 from game.version import CAMPAIGN_FORMAT_VERSION
+from .campaignairwingconfig import CampaignAirWingConfig
+from .mizcampaignloader import MizCampaignLoader
 
 
 PERF_FRIENDLY = 0
@@ -103,6 +104,14 @@ class Campaign:
             MizCampaignLoader(self.path.parent / miz, t).populate_theater()
         return t
 
+    def load_air_wing_config(self, theater: ConflictTheater) -> CampaignAirWingConfig:
+        try:
+            squadron_data = self.data["squadrons"]
+        except KeyError:
+            logging.warning(f"Campaign {self.name} does not define any squadrons")
+            return CampaignAirWingConfig({})
+        return CampaignAirWingConfig.from_campaign_data(squadron_data, theater)
+
     @property
     def is_out_of_date(self) -> bool:
         """Returns True if this campaign is not up to date with the latest format.