pgsql: Fix incorrect hash equality operator bug in Memoize

Fix incorrect hash equality operator bug in Memoize

In v14, because we don't have a field in RestrictInfo to cache both the
left and right type's hash equality operator, we just restrict the scope
of Memoize to only when the left and right types of a RestrictInfo are the
same.

In master we add another field to RestrictInfo and cache both hash
equality operators.

Reported-by: Jaime Casanova
Author: David Rowley
Discussion: https://postgr.es/m/20210929185544.GB24346%40ahch-to
Backpatch-through: 14

Branch
------
master

Details
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https://git.postgresql.org/pg/commitdiff/39a3105678a247bbfdc132cd95db5b515b8cd7f6

Modified Files
--------------
src/backend/nodes/copyfuncs.c | 3 ++-
src/backend/nodes/outfuncs.c | 3 ++-
src/backend/optimizer/path/joinpath.c | 31 +++++++++++++++++++++++--------
src/backend/optimizer/plan/initsplan.c | 28 ++++++++++++++++++++--------
src/backend/optimizer/util/restrictinfo.c | 6 ++++--
src/include/nodes/pathnodes.h | 5 +++--
6 files changed, 54 insertions(+), 22 deletions(-)