pgsql: Add optional pid parameter to pg_replication_origin_session_setu

Add optional pid parameter to pg_replication_origin_session_setup().

Commit 216a784829c introduced parallel apply workers, allowing multiple
processes to share a replication origin. To support this,
replorigin_session_setup() was extended to accept a pid argument
identifying the process using the origin.

This commit exposes that capability through the SQL interface function
pg_replication_origin_session_setup() by adding an optional pid parameter.
This enables multiple processes to coordinate replication using the same
origin when using SQL-level replication functions.

This change allows the non-builtin logical replication solutions to
implement parallel apply for large transactions.

Additionally, an existing internal error was made user-facing, as it can
now be triggered via the exposed SQL API.

Author: Doruk Yilmaz <doruk(at)mixrank(dot)com>
Author: Hayato Kuroda <kuroda(dot)hayato(at)fujitsu(dot)com>
Reviewed-by: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
Reviewed-by: Euler Taveira <euler(at)eulerto(dot)com>
Discussion: https://postgr.es/m/CAMPB6wfe4zLjJL8jiZV5kjjpwBM2=rTRme0UCL7Ra4L8MTVdOg@mail.gmail.com
Discussion: https://postgr.es/m/CAE2gYzyTSNvHY1+iWUwykaLETSuAZsCWyryokjP6rG46ZvRgQA@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/5b148706c5c8ffffe5662fe569a0f0bcef2351d9

Modified Files
--------------
contrib/test_decoding/Makefile | 2 +-
.../expected/parallel_session_origin.out | 79 ++++++++++++++++++++++
contrib/test_decoding/expected/replorigin.out | 3 +
contrib/test_decoding/meson.build | 1 +
.../specs/parallel_session_origin.spec | 56 +++++++++++++++
contrib/test_decoding/sql/replorigin.sql | 3 +
doc/src/sgml/func/func-admin.sgml | 23 ++++++-
src/backend/catalog/system_functions.sql | 9 ++-
src/backend/replication/logical/origin.c | 23 +++++--
src/include/catalog/catversion.h | 2 +-
src/include/catalog/pg_proc.dat | 2 +-
11 files changed, 193 insertions(+), 10 deletions(-)