Add FastAPI interface between the game and map.

A possible explanation for the infrequent CTDs we've been seeing since
adding fast forward is that QWebChannel doesn't keep a reference to the
python objects that it passes to js, so if the object is GC'd before the
front end is done with it, it crashes.

We don't really like QWebChannel anyway, so this begins replacing that
with FastAPI.

qt_ui/widgets/map/model/controlpointjs.py

@@ -5,12 +5,12 @@ from typing import Optional
 from PySide2.QtCore import Property, QObject, Signal, Slot
 from dcs import Point
 
+from game.server.leaflet import LeafletLatLon
 from game.theater import ConflictTheater, ControlPoint, ControlPointStatus, LatLon
 from game.utils import meters, nautical_miles
 from qt_ui.dialogs import Dialog
 from qt_ui.models import GameModel
 from qt_ui.windows.basemenu.QBaseMenu2 import QBaseMenu2
-from .leaflet import LeafletLatLon
 
 MAX_SHIP_DISTANCE = nautical_miles(80)