Add more columns to pg_stats, pg_stats_ext, and pg_stats_ext_exprs.

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