sql: allow INT to compare to OID

[rafiss]

An OID is just an INT, so they should be comparable.

Postgres allows this, and certain drivers create queries that attempt to
compare INTs to OIDs, so this improves compatibility.

fixes #53143

Release justification: low-risk, high benefit change that improves
compatibility with PGJDBC.
Release note (sql change): A value of type OID can now be compared to a
value of type INT.

[cockroach-teamcity]

This change is 

[jordanlewis]

that was easier than i expected! Implicit casts I think would remove the necessity for this, but we're not there yet so I think this is a good idea. (for the record, postgres uses implicit casts for this only, and doesn't have true cross-type operators for oid/int, but not sure it really matters)

jordan=# select oprleft::regtype, oprright::regtype from pg_operator where oprleft='oid'::regtype::oid;
 oprleft | oprright
---------+----------
 oid     | oid
 oid     | oid
 oid     | oid
 oid     | oid
 oid     | oid
 oid     | oid
(6 rows)

Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @jordanlewis and @solongordon)

[rafiss]

thanks for reviewing!

bors r=jordanlewis

[craig]

Build succeeded:

• GitHub CI (Cockroach)