pgsql: Dissociate btequalimage() from interval_ops, ending its deduplic

Dissociate btequalimage() from interval_ops, ending its deduplication.

Under interval_ops, some equal values are distinguishable.  One such
pair is '24:00:00' and '1 day'.  With that being so, btequalimage()
breaches the documented contract for the "equalimage" btree support
function.  This can cause incorrect results from index-only scans.
Users should REINDEX any btree indexes having interval-type columns.
After updating, pg_amcheck will report an error for almost all such
indexes.  This fix makes interval_ops simply omit the support function,
like numeric_ops does.  Back-pack to v13, where btequalimage() first
appeared.  In back branches, for the benefit of old catalog content,
btequalimage() code will return false for type "interval".  Going
forward, back-branch initdb will include the catalog change.

Reviewed by Peter Geoghegan.

Discussion: https://postgr.es/m/20231011013317.22.nmisch@google.com

Branch
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REL_16_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/bf1c21c4fad033414a99d6205118fbc4d75efa62

Modified Files
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contrib/amcheck/verify_nbtree.c          | 13 ++++++++++++-
src/backend/utils/adt/datum.c            | 14 ++++++--------
src/include/catalog/pg_amproc.dat        |  2 --
src/include/catalog/pg_opfamily.dat      |  2 +-
src/test/regress/expected/opr_sanity.out |  3 ++-
5 files changed, 21 insertions(+), 13 deletions(-)