vere: refactor origin update into serialization
vere: refactor origin update into serialization

Instead of updating the origin lane and mug prior to serializing the
packet, we now treat that as part of the serialization logic.

Since we don't want to do this always (we might want to serialize the
packet as-is), we add a flag to _ames_serialize_packet for this
behavior.

ngzax/urbit,urbit/urbit,urbit/urbit,ngzax/urbit,ngzax/urbit,ngzax/urbit,ngzax/urbit,urbit/urbit,urbit/urbit,ngzax/urbit,ngzax/urbit,urbit/urbit,urbit/urbit,urbit/urbit