Train stops should have a tabs listing interrupts using the station

[mrvn]

TL;DR

Show a tab for interrupts using the train stop as a condition or as a target in the train stop GUI.

Why?

Train stops show the list of trains having the station in the schedule. But with interrupts the station won't be in the schedule unless the interrupt triggers, or not at all with conditions. This makes it hard to find out if a train stop is still being used. It would also simplify modifying interrupts using that station when the station changes, e.g. for the item count condition.