pgsql: Update information_schema definition for not-null constraints

Update information_schema definition for not-null constraints

Now that we have catalogued not-null constraints, our information_schema
definition can be updated to grab those rather than fabricate synthetic
definitions.

Note that we still don't have catalog rows for not-null constraints on
domains, but we've never had not-null constraints listed in
information_schema, so that's a problem to be solved separately.

Co-authored-by: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Co-authored-by: Álvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://postgr.es/m/81b461c4-edab-5d8c-2f88-203108425340@enterprisedb.com
Discussion: https://postgr.es/m/202309041710.psytrxlsiqex@alvherre.pgsql

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/3af7217942722369a6eb7629e0fb1cbbef889a9b

Modified Files
--------------
src/backend/catalog/information_schema.sql | 74 +++++++++++-------------------
src/include/catalog/catversion.h           |  2 +-
2 files changed, 28 insertions(+), 48 deletions(-)