Enhance postgres protocol parsing to handle ParameterStatus message

[ddelnano]

Users have requested that they'd like to be able to see the postgres server version from the pgsql protocol tracing. This is something that postgres encodes in the ParameterStatus message.

The postgres parser knows the ParameterStatus message exists, but we aren't pulling out the details from the payload when we see the message (the Tag::kParamStatus is missing from this switch statement).