New space platform wait condition for outgoing requests satisfied

[nzer]

Currently if you have a space platform that is intended to provide some item to a planet or another platform, there isn't a good way to get it to wait until it's fulfilled that request. You can set it to wait for inactivity, but this will cause it to wait longer than necessary, and without careful tuning it may leave without fully delivering the items or even leave without delivering any of them.

For example, say the pad on Nauvis is requesting 1000 green belts, and your Vulcanus freighter arrives with 1000 green belts in storage and a 10 second inactivity wait condition. In the happy path, your freighter will immediately launch all 1000 belts, then will pointlessly wait for 10 additional seconds while the timer ticks down, before leaving. In the unhappy path, all of the landing pad's input ports may be busy with other deliveries while the inactivity timer ticks down. In that scenario the freighter will just leave, having delivered nothing.

That should never happen. This particular use case is the entire reason why space platforms exist, so it should be well supported. If the platform knows it can satisfy an active request, either from the planet or another platform, there should be a wait condition it can use to wait until it has done so. Or the goods should be immediately flagged as on the way even if the platform is temporarily blocked on actually delivering them, so that a short inactivity timer is workable.