One really rough thing about how we did onchain fees is that the records update
every time a new event comes in.
The better way to do this is to create new entries for every adjustment,
so that reconciliation between printouts isn't a misery.
We add a timestamp and `update_count` to these records, so you can
roughly order them now (and have a good idea of the last time an event
that updated an onchain_fee occurred).
