pgsql: pg_createsubscriber: Add -R publications option.

pg_createsubscriber: Add -R publications option.

This patch introduces a new '-R'/'--remove' option in the
'pg_createsubscriber' utility to specify the object types to be removed
from the subscriber. Currently, we add support to specify 'publications'
as an object type. In the future, other object types like failover-slots
could be added.

This feature allows optionally to remove publications on the subscriber
that were replicated from the primary server (before running this tool)
during physical replication. Users may want to retain these publications
in case they want some pre-existing subscribers to point to the newly
created subscriber.

Author: Shubham Khanna <khannashubham1197(at)gmail(dot)com>
Reviewed-by: Peter Smith <smithpb2250(at)gmail(dot)com>
Reviewed-by: David G. Johnston <david(dot)g(dot)johnston(at)gmail(dot)com>
Reviewed-by: Euler Taveira <euler(at)eulerto(dot)com>
Reviewed-by: Zhijie Hou <houzj(dot)fnst(at)fujitsu(dot)com>
Reviewed-by: vignesh C <vignesh21(at)gmail(dot)com>
Reviewed-by: Nisha Moond <nisha(dot)moond412(at)gmail(dot)com>
Reviewed-by: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
Discussion: https://postgr.es/m/CAHv8RjL4OvoYafofTb_U_JD5HuyoNowBoGpMfnEbhDSENA74Kg@mail.gmail.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/e5aeed4b8020424fa882c3d1969d00c2b2d8cf30

Modified Files
--------------
doc/src/sgml/ref/pg_createsubscriber.sgml | 23 +++++
src/bin/pg_basebackup/pg_createsubscriber.c | 105 ++++++++++++++++++---
src/bin/pg_basebackup/t/040_pg_createsubscriber.pl | 25 ++++-
3 files changed, 136 insertions(+), 17 deletions(-)