Move nevent threshold to finalsink

With !176 (merged), we now record nevent and livetimes in finalsink. As such, we can now set FAR upstream, record FAR of all zerolags out of finalsink, and check the nevent of the 1w stats when choosing to upload a trigger.

This MR does just that to keep things simple, but the next change will add command line args to set an nevent/livetime threshold on each timescale. We then just need to decide if All timescales should wait for 1m points on 1w, or other conditions like that.

This change will be included in a branch off spiir-O4-review-v3 as a patch.