pgsql: Fix miscellaneous issues in EXCEPT publication clause.

Fix miscellaneous issues in EXCEPT publication clause.

Improve documentation regarding multiple publications and partition
hierarchies. Refine error reporting for excluded relations. Consolidate
docs by using table_object instead of expanded table syntax in publication
commands. Also includes minor test cleanup and naming fixes.

Reported-by: Peter Smith <smithpb2250(at)gmail(dot)com>
Author: vignesh C <vignesh21(at)gmail(dot)com>
Reviewed-by: Peter Smith <smithpb2250(at)gmail(dot)com>
Reviewed-by: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
Discussion: https://postgr.es/m/CALDaNm1CiBYcteE_jjPA4BPHfX30dg9eTTTkJgkjY5tgE7t=bQ@mail.gmail.com
Discussion: https://postgr.es/m/CALDaNm3=JrucjhiiwsYQw5-PGtBHFONa6F7hhWCXMsGvh=tamA@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/6b0550c45d132c7a75acf98cb76f8a43bf5e94df

Modified Files
--------------
doc/src/sgml/ref/alter_publication.sgml | 4 ++--
doc/src/sgml/ref/create_publication.sgml | 6 +++---
src/backend/catalog/pg_publication.c | 2 +-
src/test/regress/expected/publication.out | 2 +-
src/test/subscription/t/037_except.pl | 24 ++++++++++++------------
5 files changed, 19 insertions(+), 19 deletions(-)