Add option to override obs_id in SimTelEventSource

[maxnoe]

Simulations were performed that re-use the same CORSIKA run numbers, e.g. different pointing positions for the same particles in prod5 and also different particles for the same pointing.

To still enable unique obs_ids in merged files for these productions, an "override_obs_id" option is added to the SimTelEventSource that can be used to assign new, globally unique ids.

The original run number is added to the SimulationConfigContainer.

We have discussed before to decouple simulation obs_ids from CORSIKA / simtel run numbers.

This is a first step in enabling this. This was triggered also because the LST MC production reuses run numbers in a way that completely prevented merging files for model training.

[kosack]

yes, this fits well with the external discussion you mentioned that obs_ids should be decoupled from simulation run_ids.

is a config option enough? It means computing the unique obs_id outside the tool, in a script for example. Another option is to have the obs_id by default be in the agreed ACADA format (run_number + 4000000 or whatever), and then override_obs_id can be used only in special cases where you don't want that behavior

[maxnoe]

I need this now for really the case where I need to assign custom obs_ids. The LST simulations restart run numbers for each pointing and I need to merge ~10 pointing directions for model training.

I wouldn't just add the 4, since ctapipe is used on not just SDMC-DPPS produced simtel files, in fact, no such files really exist as of now.