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/waypointjs.py

@@ -7,10 +7,10 @@ from PySide2.QtCore import Property, QObject, Signal, Slot
 
 from game.ato import Flight, FlightWaypoint
 from game.ato.flightwaypointtype import FlightWaypointType
+from game.server.leaflet import LeafletLatLon
 from game.theater import ConflictTheater, LatLon
 from gen.flights.flightplan import FlightPlan
 from qt_ui.models import AtoModel
-from .leaflet import LeafletLatLon
 
 if TYPE_CHECKING:
     from .flightjs import FlightJs