pgsql: Reject REPLICA IDENTITY USING INDEX on column with invalid NOT N

Reject REPLICA IDENTITY USING INDEX on column with invalid NOT NULL

ALTER TABLE ... REPLICA IDENTITY USING INDEX verified key columns by
reading pg_attribute.attnotnull, but commit a379061a22a8 made
attnotnull true also for unvalidated (NOT VALID) not-null constraints,
which do not prove the column null-free. An index over such a column
could thus be marked as replica identity even though the column might
contain NULLs, causing apply-side divergence for UPDATE/DELETE on the
nullable rows.

Fix by additionally requiring convalidated for the underlying
constraint, mirroring the fix d9ffc27291f applied to ATExecAddIdentity
for the analogous identity-column case.

Author: Ante Krešić <ante(at)tigerdata(dot)com>
Reviewed-by: Aleksander Alekseev <aleksander(at)tigerdata(dot)com>
Reviewed-by: solai v <solai(dot)cdac(at)gmail(dot)com>
Backpatch-through: 18
Discussion: https://postgr.es/m/CABXQ4dJUibZzN91qvWmsfA7MUDn9YRCNyu3CcukdyokbH1=41Q@mail.gmail.com

Branch
------
REL_19_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/82c86ac6822033cff10a39496925c02ca7adc532

Modified Files
--------------
src/backend/commands/tablecmds.c | 22 ++++++++++++++++++++++
src/test/regress/expected/replica_identity.out | 23 +++++++++++++++++++++++
src/test/regress/sql/replica_identity.sql | 16 ++++++++++++++++
3 files changed, 61 insertions(+)