psql: Show comments in \dRp+, \dRs+, and \dX+ psql meta-commands.

psql: Show comments in \dRp+, \dRs+, and \dX+ psql meta-commands.

Previously, the psql meta-commands that list publications, subscriptions,
and extended statistics did not display their associated comments,
whereas other \d meta-commands did. This made it inconvenient for users
to view these objects together with their descriptions.

This commit improves \dRp+ and \dRs+ to include comments for publications
and subscriptions. It also extends the \dX meta-command to accept the + option,
allowing comments for extended statistics to be shown when requested.

Author: Fujii Masao <masao.fujii@gmail.com>
Co-authored-by: Jim Jones <jim.jones@uni-muenster.de>
Reviewed-by: Matheus Alcantara <matheusssilv97@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/CAHGQGwGL4JqiKA26fnGx-cTM=VzoTs_uzqejvj4Fawyr4uLUUw@mail.gmail.com