Fix SoftwareTrigger for actual simtel files

[maxnoe]

Fixes #2321

[Tobychev]

I can't tell what was wrong, the linked issue helps somewhat, but even that doesn't actually say what the resulting error is so I've no idea if this PR will solve it 🤷‍♂️

[maxnoe]

@Tobychev not sure how to improve that, since:

• the issue contains the actual reason for the Bug (assuming a python list vs. sources producing a numpy array)

• this PR adds new tests testing both an artificial case (with lists and arrays) and one using a simtel event file as input.

What else is needed?

[maxnoe]

If you want to make sure, run the new tests with the code on Main, they fail with the error described in the issue

[maxnoe]

@Tobychev I updated the issue description with the full error message.