pgsql: Fix determination of not-null constraint "locality" for inherite

Fix determination of not-null constraint "locality" for inherited columns

It is possible to have a non-inherited not-null constraint on an
inherited column, but we were failing to preserve such constraints
during pg_upgrade where the source is 17 or older, because of a bug in
the pg_dump query for it.  Oversight in commit 14e87ffa5c54.  Fix that
query.  In passing, touch-up a bogus nearby comment introduced by the
same commit.

In version 17, make the regression tests leave a table in this
situation, so that this scenario is tested in the cross-version upgrade
tests of 18 and up.

Author: Dilip Kumar <dilipbalaut@gmail.com>
Reported-by: Andrew Bille <andrewbille@gmail.com>
Bug: #19074
Backpatch-through: 18
Discussion: https://postgr.es/m/19074-ae2548458cf0195c@postgresql.org

Branch
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REL_17_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/c945b06d5f03e30cec279df516688c70787b2b2c

Modified Files
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src/test/regress/expected/constraints.out | 4 ++++
src/test/regress/sql/constraints.sql      | 5 +++++
2 files changed, 9 insertions(+)