Stress test bugs

[robot256]

• [x] Before dispatching train, make sure Global Stop is actually connected to a rail segment.
• [x] A train dispatched through the elevator, set to manual before arriving, and then driven back through the elevator will crash in "schedule_temp_stop". Need to check that you've arrived on the correct surface before creating temp stops.
• [x] Don't erase the empty trains_pathing list from group[].global_stops[] entries.
• [x] Make the group[].global_stops[].trains_arriving entry a simple LuaEntity (or nil) instead of a list, since there should only be one train arriving at a time.
• [x] Figure out how to tell when a train is switched to manual mode not by the elevator, and should be removed from the reservation/pathing list.
• [ ] Purge train from "pathing" list if the next non-temporary stop is not in the group.
• [ ] Purge train from "arriving" if the next stop is not in the group (there should not be any temporary stop left).
• [ ] Purge train from "arriving" and "waiting" if we are trying to add it to a "pathing" group.
• [x] Major bug happens when the elevator gets crowded. When a train is partially through or waiting for the space elevator. If it completes the temporary stop to the elevator but doesn't get teleported immediately, it switches to "destination full" and "waiting" and "dispatched" every tick.
• [x] Problem: stop_group.reserve_stop() is getting called when train arrives at elevator temporary stop? When it just got out of the elevator after being stuck.
• [x] The stuck steel train, what position is the schedule before it teleports?
• [x] why did the elevator event seem to fire before the loco actually went through?
• [x] In on_init, scan surfaces for existing elevators and register them.
• [ ] When an elevator is removed, scan for remaining elevators to use instead. Problem: We get the event for elevator destruction before SE has a chance to remove the hidden stops, so when we scan for stops, they are still there.

[suisseWalter]

dummy_space_test_extra_train.zip I was somehow able to create a set of trains where they think the stations don't have enough space but they both have enough space. I have a space station with 5 slots and a ground station with 3 slots. and in total 6 trains. that should be more then enough for all of them to move between the two stations. somehow they don't. both ends think that they can't move. It might have been caused by editing the proxy stops while some train have already tried to path to them etc. not sure if you need more info. (and not sure if I can exactly reproduce it.

[robot256]

Well, the first problem is that there was no proxy stop called "testnauvis" in orbit, so the train in orbit never got registered as waiting to go to the surface.

Second problem is as you suspected. There were multiple trains registered in multiple states for both stops. I actually think it's because there is no schedule condition arriving at the Global Stops, so the train doesn't change states properly as it arrives. It doesn't get removed from the "pathing" or "arriving" state at one stop before getting added to the other stop. Thanks for some more edge cases to test.