Add frozen combat modelling.

This doesn't do anything yet, but sets up the data model handling for
frozen combat. The next step is to show combat in the map view, since
that will be helpful when debugging the step after that one: resolving
frozen combat.

This would benefit from caching the Shapely data for SAM threat zones.
Right now it's generating them once per tick and the stuttering is
visible at max speed.

https://github.com/dcs-liberation/dcs_liberation/issues/1680

game/utils.py

@@ -7,6 +7,9 @@ from collections.abc import Iterable
 from dataclasses import dataclass
 from typing import TypeVar, Union
 
+from dcs import Point
+from shapely.geometry import Point as ShapelyPoint
+
 METERS_TO_FEET = 3.28084
 FEET_TO_METERS = 1 / METERS_TO_FEET
 NM_TO_METERS = 1852
@@ -280,3 +283,7 @@ def interpolate(value1: float, value2: float, factor: float, clamp: bool) -> flo
         return min(bigger_value, max(smaller_value, interpolated))
     else:
         return interpolated
+
+
+def dcs_to_shapely_point(point: Point) -> ShapelyPoint:
+    return ShapelyPoint(point.x, point.y)