Convert escort request to a waypoint property.

Another step in reducing the rigidity of FlightPlan and making it
testable.

There is one intentional behavior change here: escort flights no longer
request escorts. That actually has a very minimal effect because these
properties are only used for two things: determining if a package needs
escorts or not, and determining when the TARCAP should show up and
leave. Since escorts won't have been in the package when the first part
happens anyway, that has no effect. The only change is that TARCAP won't
show up earlier or stay later just because of a TOT offset for an escort
flight.

game/ato/flightwaypoint.py

@@ -41,6 +41,8 @@ class FlightWaypoint:
     # The minimum amount of fuel remaining at this waypoint in pounds.
     min_fuel: float | None = None
 
+    wants_escort: bool = False
+
     actions: list[WaypointAction] = field(default_factory=list)
     options: dict[str, WaypointOption] = field(default_factory=dict)