tests: improve fuzzer by including new features in the generated tests

[eckter]

There's a few things lacking with the fuzzer, new features that haven't been added to the generated scenarios:

• stdcm: we can request time for start or end points
• pathfinding locations can be defined as operational points for more realistic paths
• we can add scheduled points (though it's difficult to generate realistic times)

A little less clear:

We could tweak the script to be usable with an imported timetable. We wouldn't necessarily need to include the timetable data in the generated json.