Enable logging both "from" and "to" socket

Enable logging both "from" and "to" socket

Change the function prototype for dns_message_logfmtpacket() so that it
takes two isc_sockaddr_t parameters: one for the sending side and
another one for the receiving side.  This enables debug messages to be
more precise.

Also adjust the function prototype for logfmtpacket() accordingly.
Unlike dns_message_logfmtpacket(), this function must not require both
'from' and 'to' parameters to be non-NULL as it is still going to be
used by dns_message_logpacket(), which only provides a single socket
address.  Adjust its log format to handle both of these cases properly.

Adjust both dns_message_logfmtpacket() call sites accordingly, without
actually providing the second socket address yet.  (This causes the
revised REQUIRE() assertion in dns_message_logfmtpacket() to fail; the
issue will be addressed in a separate commit.)