Rethink the logging of BridgeDB

Now that we are playing around with BridgeDB, it's probably a good idea to also improve its logging.

For example, BridgeDB currently doesn't have any debug logs during descriptor parsing (which made it harder to find the root of #9174 (moved)).

Also, we should make sure that BridgeDB can scrub client's IPs from the logs (even for debug logs). Example of offending logs: Valid recaptcha from ... and [DEBUG] getBridgesForIP(, ...)

Also, maybe we should consider using Tor's extended nicknames to improve log greppability. Extended nicknames combine the identity digest and the nickname of a router in the same line. Example: $AAAAAAAA01234AAAAAAAAAAAAAAAAAAAAAAAAAAA=fred .

Check Tor's function node_get_verbose_nickname() and https://gitweb.torproject.org/torspec.git/blob/HEAD:/control-spec.txt#l152

We should also identify other information that the BridgeDB operator would be interested in and log them (maybe even write a heartbeat log with statistics).