pgsql: Split the SetSubscriptionRelState function into two

Split the SetSubscriptionRelState function into two

We don't actually need the insert-or-update logic, so it's clearer to
have separate functions for the inserting and updating.

Author: Petr Jelinek <petr.jelinek@2ndquadrant.com>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/bcf79b5bb648d30696406034a61ce0ca3dcb0dea

Modified Files
--------------
src/backend/catalog/pg_subscription.c       | 129 ++++++++++++++++------------
src/backend/commands/subscriptioncmds.c     |   8 +-
src/backend/replication/logical/tablesync.c |  34 ++++----
src/include/catalog/pg_subscription_rel.h   |   6 +-
4 files changed, 96 insertions(+), 81 deletions(-)