Use first event time in update catalog script

[morcuended]

Also some cleanup is done.

Closes #262

[marialainez]

Isn't the format and scale of the dragon_time the same as that of the times in the run_start column?

[morcuended]

Isn't the format and scale of the dragon_time the same as that of the times in the run_start column?

good point, I would have to check again

[morcuended]

Isn't the format and scale of the dragon_time the same as that of the times in the run_start column?
No, run_start in the summary was defined like

run_start = int(round(Time(f.camera_config.date, format="unix").unix_tai)) * int(1e9)

The proper way of getting the eventwise timestamps from dragon_time is using time = (timestamp, format="unix", scale="utc"). Then, getting the ISO format in UTC scale as time.utc.iso (to make sure to use UTC scale). So I think it is fine as it is now

[morcuended]

To make the tests pass you need to merge the current main version to force the usage of lstchain >=v0.10.5