Add the database name to the ps display of logical WAL senders

Add the database name to the ps display of logical WAL senders

Logical WAL senders display now as follows, gaining a database name:
postgres: walsender USER DATABASE HOST(PORT) STATE

Physical WAL senders show up the same, as of:
postgres: walsender USER HOST(PORT) STATE

This information was missing, hence it was not possible to know from ps
if a WAL sender was a logical or a physical one, and on which database
it is connected when it is logical.

Author: Tatsuhiro Nakamori
Reviewed-by: Fujii Masao, Bharath Rupireddy
Discussion: https://postgr.es/m/36a3b137e82e0ea9fe7e4234f03b64a1@oss.nttdata.com