pg_createsubscriber: Add '--all' option.

pg_createsubscriber: Add '--all' option.

The '--all' option indicates that the tool queries the source server
(publisher) for all databases and creates subscriptions on the target
server (subscriber) for databases with matching names. Without this user
needs to explicitly specify all databases by using -d option for each
database.

This simplifies converting a physical standby to a logical subscriber,
particularly during upgrades.

The options '--database', '--publication', '--subscription', and
'--replication-slot' cannot be used when '--all' is specified.

Author: Shubham Khanna <[email protected]>
Reviewed-by: vignesh C <[email protected]>
Reviewed-by: Ashutosh Bapat <[email protected]>
Reviewed-by: Euler Taveira <[email protected]>
Reviewed-by: Hayato Kuroda <[email protected]>
Reviewed-by: Amit Kapila <[email protected]>
Reviewed-by: Peter Smith <[email protected]>
Reviewed-by: Shlok Kyal <[email protected]>
Discussion: https://postgr.es/m/CAHv8RjKhA=_h5vAbozzJ1Opnv=KXYQHQ-fJyaMfqfRqPpnC2bA@mail.gmail.com