Commit f56f8f8da6 added some code in CloneFkReferencing that's way too
lax about a Constraint node it manufactures, not initializing enough
struct members -- initially_valid in particular was forgotten. This
causes some FKs in partitions added by ALTER TABLE ATTACH PARTITION to
be marked as not validated. Set initially_valid true, which fixes the
bug.
While at it, make the struct initialization more complete. Very similar
code was added in two other places by the same commit; make them all
follow the same pattern for consistency, though no bugs are apparent
there.
This bug has never been reported: I only happened to notice while
working on commit 614a406b4f. The test case that was added there with
the improper result is repaired.
Backpatch to 12.
Discussion: https://postgr.es/m/20221005105523.bhuhkdx4olajboof@alvherre.pgsql
b0284bfb1d