Add option to fast forward to first contact.

This is the first step in a larger project to add play/pause buttons to
the Liberation UI so the mission can be generated at any point.
docs/design/turnless.md describes the plan.

This adds an option to fast forward the turn to first contact before
generating the mission. None of that is reflected in the UI (for now),
but the miz will be generated with many flights in the air.

For now "first contact" means as soon as any flight reaches its IP. I'll
follow up to add threat checking so that air-to-air combat also triggers
this, as will entering a SAM's threat zone.

This also includes an option to halt fast-forward whenever a player
flight reaches a certain mission-prep phase. This can be used to avoid
fast forwarding past the player's startup time, taxi time, or takeoff
time. By default this option is disabled so player aircraft may start in
the air (possibly even at their IP if they're the first mission to reach
IP).

Fuel states do not currently account for distance traveled during fast
forward. That will come later.

https://github.com/dcs-liberation/dcs_liberation/issues/1681

gen/flights/flightplan.py

@@ -43,11 +43,11 @@ from .closestairfields import ObjectiveDistanceCache
 from game.ato.flighttype import FlightType
 from game.ato.flightwaypointtype import FlightWaypointType
 from game.ato.flightwaypoint import FlightWaypoint
-from game.ato.flight import Flight
 from .traveltime import GroundSpeed, TravelTime
 from .waypointbuilder import StrikeTarget, WaypointBuilder
 
 if TYPE_CHECKING:
+    from game.ato.flight import Flight
     from game.ato.package import Package
     from game.coalition import Coalition
     from game.threatzones import ThreatZones

gen/flights/traveltime.py

@@ -6,19 +6,17 @@ from datetime import timedelta
 from typing import TYPE_CHECKING
 
 from dcs.mapping import Point
-from dcs.unittype import FlyingType
 
 from game.utils import (
     Distance,
     SPEED_OF_SOUND_AT_SEA_LEVEL,
     Speed,
-    kph,
     mach,
     meters,
 )
-from game.ato.flight import Flight
 
 if TYPE_CHECKING:
+    from game.ato.flight import Flight
     from game.ato.package import Package
 
 

gen/flights/waypointbuilder.py

@@ -18,10 +18,6 @@ from dcs.mapping import Point
 from dcs.unit import Unit
 from dcs.unitgroup import VehicleGroup, ShipGroup
 
-if TYPE_CHECKING:
-    from game.coalition import Coalition
-    from game.transfers import MultiGroupTransport
-
 from game.theater import (
     ControlPoint,
     MissionTarget,
@@ -31,7 +27,11 @@ from game.theater import (
 from game.utils import Distance, meters, nautical_miles
 from game.ato.flightwaypointtype import FlightWaypointType
 from game.ato.flightwaypoint import FlightWaypoint
-from game.ato.flight import Flight
+
+if TYPE_CHECKING:
+    from game.ato.flight import Flight
+    from game.coalition import Coalition
+    from game.transfers import MultiGroupTransport
 
 
 @dataclass(frozen=True)