pgsql: Add PublicationTable and PublicationRelInfo structs

Add PublicationTable and PublicationRelInfo structs

These encapsulate a relation when referred from replication DDL.
Currently they don't do anything useful (they're just wrappers around
RangeVar and Relation respectively) but in the future they'll be used to
carry column lists.

Extracted from a larger patch by Rahila Syed.

Author: Rahila Syed <rahilasyed90(at)gmail(dot)com>
Reviewed-by: Álvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
Reviewed-by: Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>
Reviewed-by: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
Discussion: https://postgr.es/m/CAH2L28vddB_NFdRVpuyRBJEBWjz4BSyTB=_ektNRH8NJ1jf95g@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/0c6828fa987b791744b9c8685aadf1baa21f8977

Modified Files
--------------
src/backend/catalog/pg_publication.c | 10 +++----
src/backend/commands/publicationcmds.c | 53 ++++++++++++++++++++++------------
src/backend/nodes/copyfuncs.c | 12 ++++++++
src/backend/nodes/equalfuncs.c | 11 +++++++
src/backend/parser/gram.y | 26 +++++++++++++----
src/include/catalog/pg_publication.h | 7 ++++-
src/include/nodes/nodes.h | 1 +
src/include/nodes/parsenodes.h | 5 ++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 95 insertions(+), 31 deletions(-)