Add temporal FOREIGN KEY contraints

Add temporal FOREIGN KEY contraints

Add PERIOD clause to foreign key constraint definitions.  This is
supported for range and multirange types.  Temporal foreign keys check
for range containment instead of equality.

This feature matches the behavior of the SQL standard temporal foreign
keys, but it works on PostgreSQL's native ranges instead of SQL's
"periods", which don't exist in PostgreSQL (yet).

Reference actions ON {UPDATE,DELETE} {CASCADE,SET NULL,SET DEFAULT}
are not supported yet.

(previously committed as 34768ee3616, reverted by 8aee330af55; this is
essentially unchanged from those)

Author: Paul A. Jungwirth <[email protected]>
Reviewed-by: Peter Eisentraut <[email protected]>
Reviewed-by: jian he <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CA+renyUApHgSZF9-nd-a0+OPGharLQLO=mDHcY4_qQ0+noCUVg@mail.gmail.com