Like with deleting waypoints, these will degrade the flight plan to the
2.1 behavior.
Ascend/descend points aren't in use any more, so I removed those.
Previously we were trying to make every potential flight plan look
just like a strike mission's flight plan. This led to a lot of special
case behavior in several places that was causing us to misplan TOTs.
I've reorganized this such that there's now an explicit `FlightPlan`
class, and any specialized behavior is handled by the subclasses.
I've also taken the opportunity to alter the behavior of CAS and
front-line CAP missions. These no longer involve the usual formation
waypoints. Instead the CAP will aim to be on station at the time that
the CAS mission reaches its ingress point, and leave at its egress
time. Both flights fly directly to the point with a start time
configured for a rendezvous.
It might be worth adding hold points back to every flight plan just to
ensure that non-formation flights don't end up with a very low speed
enroute to the target if they perform ground ops quicker than
expected.
Also fixes the CAP racetracks so the AI actually stays on station.
Waypoint TOT assignment happens at mission generation time for the
sake of the UI. It's a bit messy since we have the late-initialized
field in FlightWaypoint, but on the other hand we don't have to reset
every extant waypoint whenever the player adjusts the mission's TOT.
If we want to clean this up a bit more, we could have two distinct
types for waypoints: one for the planning stage and one with the
resolved TOTs. We already do some thing like this with Flight vs
FlightData.
Future improvements:
* Estimate the group's ground speed so we don't need such wide margins
of error.
* Delay takeoff to cut loiter fuel cost.
* Plan mission TOT based on the aircraft in the package and their
travel times to the objective.
* Tune target area time prediction. Flights often don't need to travel
all the way to the target point, and probably won't be doing it
slowly, so the current planning causes a lot of extra time spent in
enemy territory.
* Per-flight TOT offsets from the package to allow a sweep to arrive
before the rest, etc.
