New event: on_spidertron_command_cancelled

[Xorimuth]

Alternatively named on_spidertron_command_interrupted

Similar to viewtopic.php?f=65&t=88668, but for when the spidertron's autopilot_destination has been removed before it gets there, such as when a player driving a spidertron presses a movement key.

I don't mind if it also gets triggered because spidertron is destroyed, or because the player has issued a new command, because those can be detected from within the event and dealt with.

I'd use this with https://mods.factorio.com/mod/SpidertronWaypoints in order to cancel all existing waypoints on the event. Currently I am checking every spidertron in on_nth_tick to see if it has lost its autopilot_destination.

[Xorimuth]

I guess that it would still be nice to have, but I have a fairly neat (and perfectly behaved as far I can tell) workaround here: https://github.com/tburrows13/Spidertro ... #L396-L407
(with the custom controls being defined here: https://github.com/tburrows13/Spidertro ... #L114-L137)