Add livery selection dropdown to air wing config.

Fixes https://github.com/dcs-liberation/dcs_liberation/issues/1861.

qt_ui/widgets/combos/liveryselector.py

@@ -0,0 +1,31 @@
+from __future__ import annotations
+
+from PySide6.QtWidgets import QComboBox
+from dcs.liveries.livery import Livery
+
+from game.squadrons import Squadron
+
+
+class LiverySelector(QComboBox):
+    def __init__(self, squadron: Squadron) -> None:
+        super().__init__()
+        self.setSizeAdjustPolicy(QComboBox.SizeAdjustPolicy.AdjustToContents)
+        self.set_squadron(squadron)
+
+    @property
+    def selected_livery(self) -> Livery | None:
+        return self.currentData()
+
+    def set_squadron(self, squadron: Squadron) -> None:
+        selected_idx: int | None = None
+        self.clear()
+        self.addItem("Default", None)
+        for idx, livery in enumerate(
+            squadron.aircraft.dcs_unit_type.iter_liveries_for_country(squadron.country)
+        ):
+            self.addItem(livery.name, livery)
+            if squadron.livery == livery.id:
+                selected_idx = idx
+        if selected_idx is not None:
+            self.setCurrentIndex(selected_idx)
+        self.update()