Add: adhere the autosave_on_exit setting for Null videodriver #9343
Motivation / Problem
Our scripting stuff is rarely useful, but I now had a use, it wasn't supplying.
For automated testing, I want to load an (old) savegame, run for a few ticks, and save&exit, so I could compare it with later results.
But .. there is no way to do this "run for a few ticks, and save&exit" currently. I could see two possible solutions:
I went with 3), as 2) felt weird and dirty. 1) would be ideal, but is a lot more work.
Checklist for review
Some things are not automated, and forgotten often. This list is a reminder for the reviewers.