BridgeDB networkstatus descriptor parsers need refactoring

Some of this stuff I am not sure if it was part of some super old proposal for some descriptor type. Other stuff is just janky. For example, one of the bugs I just found, on L469 in lib/bridgedb/Bridges.py, wouldn't ever get hit because to my knowledge BridgeDB has never handed out fingerprints. But if it were to, with those lines, it would hand out PT bridges that look like this:

bridge obfs3 1.2.3.4:5555 keyid=0123456789abcdef0123456789abcdef01234567

with the part after keyid= being the bridge's fingerprint.

Another thing which I am currently looking into is BridgeDB's parsing of the networkstatus files, it seems BridgeDB expects there to always be an a line with the ORaddress, whereas this is only the case if the bridge has at least one IPv6 address.

BridgeDB also seems to think that a bridge/relay can't have more than 8 ORaddress:ORport pairs. I remember this discussed years ago, though I thought it was 16, and I don't recall if it was ever implemented in little-t tor.

In short, there is quite a bit of jankiness in BridgeDB's descriptor parsing. I am going to continue fixing things and referencing dir-spec.txt when there is a discrepancy, and just calling BridgeDB out when there appears to be no sane reason for something referenced in any of torspec.