pgsql: Add more columns to pg_stats, pg_stats_ext, and pg_stats_ext_exp

Add more columns to pg_stats, pg_stats_ext, and pg_stats_ext_exprs.

This commit adds table OID and attribute number columns to
pg_stats, and it adds table OID and statistics object OID columns
to pg_stats_ext and pg_stats_ext_exprs. A proposed follow-up
commit would use pg_stats.tableid to simplify a query in pg_dump.
The others have no immediate purpose but may be useful later.

Bumps catversion.

Author: Corey Huinker <corey(dot)huinker(at)gmail(dot)com>
Reviewed-by: Sami Imseih <samimseih(at)gmail(dot)com>
Reviewed-by: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Reviewed-by: Michael Paquier <michael(at)paquier(dot)xyz>
Discussion: https://postgr.es/m/CADkLM%3DcoCVy92QkVUUTLdo5eO2bMDtwMrzRn_8miAhX%2BuPaqXg%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/3b88e50d6c2ef972748378a10fc444efae90ed14

Modified Files
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doc/src/sgml/system-views.sgml | 60 ++++++++++++++++++++++++++++++
src/backend/catalog/system_views.sql | 6 +++
src/include/catalog/catversion.h | 2 +-
src/test/regress/expected/rules.out | 6 +++
src/test/regress/expected/stats_import.out | 4 +-
5 files changed, 75 insertions(+), 3 deletions(-)