Bridgestrap should export bulk sanitized state for Collector

In https://gitlab.torproject.org/tpo/metrics/collector/-/issues/40002 we learn that Collector wants to archive bridgestrap's state over time. This plan sounds useful.

I can imagine two good ways to achieve this goal:

• Have bridgestrap generate an output page which has a stanza for each bridge it has tested, but which only lists hashed fingerprints and no IP addresses so it's safe for everybody to see, and then serve that page somewhere so Collector can archive it periodically. That's this ticket.

Or,

• Add bridgestrap's status info to what rdsys already exports, so then Collector would pick it up already by collecting rdsys's periodic state snapshots. If this is the better way to go, please close this ticket and open that one. :)

Thanks!