Enhance pg_stat_wal_receiver view to display host and port of sender server.

Enhance pg_stat_wal_receiver view to display host and port of sender server.

Previously there was no way in the standby side to find out the host and port
of the sender server that the walreceiver was currently connected to when
multiple hosts and ports were specified in primary_conninfo. For that purpose,
this patch adds sender_host and sender_port columns into pg_stat_wal_receiver
view. They report the host and port that the active replication connection
currently uses.

Bump catalog version.

Author: Haribabu Kommi
Reviewed-by: Michael Paquier and me
Discussion: https://postgr.es/m/CAJrrPGcV_aq8=cdqkFhVDJKEnDQ70yRTTdY9RODzMnXNrCz2Ow@mail.gmail.com