reg* checks in pg_upgrade are out of date

Hi,

It seems the list of reg* types and the check for them in pg_upgrade
have gone out of sync. We have the following reg* types:

 SELECT typname FROM pg_type WHERE typname LIKE 'reg%' order by typname;
┌───────────────┐
│    typname    │
├───────────────┤
│ regclass      │
│ regconfig     │
│ regdictionary │
│ regnamespace  │
│ regoper       │
│ regoperator   │
│ regproc       │
│ regprocedure  │
│ regrole       │
│ regtype       │
└───────────────┘
(10 rows)

but pg_upgrade doesn't consider all of them:

        /*
         * While several relkinds don't store any data, e.g. views, they can
         * be used to define data types of other columns, so we check all
         * relkinds.
         */
        res = executeQueryOrDie(conn,
                                "SELECT n.nspname, c.relname, a.attname "
                                "FROM   pg_catalog.pg_class c, "
                                "       pg_catalog.pg_namespace n, "
                                "       pg_catalog.pg_attribute a "
                                "WHERE  c.oid = a.attrelid AND "
                                "       NOT a.attisdropped AND "
                                "       a.atttypid IN ( "
                                "           'pg_catalog.regproc'::pg_catalog.regtype, "
                                "           'pg_catalog.regprocedure'::pg_catalog.regtype, "
                                "           'pg_catalog.regoper'::pg_catalog.regtype, "
                                "           'pg_catalog.regoperator'::pg_catalog.regtype, "
        /* regclass.oid is preserved, so 'regclass' is OK */
        /* regtype.oid is preserved, so 'regtype' is OK */
                                "           'pg_catalog.regconfig'::pg_catalog.regtype, "
                                "           'pg_catalog.regdictionary'::pg_catalog.regtype) AND "
                                "       c.relnamespace = n.oid AND "
                                "       n.nspname NOT IN ('pg_catalog', 'information_schema')");

(I don't get the order here btw)

ISTM when regrole and regnamespace were added, pg_upgrade wasn't
considered. It turns out that regrole is safe, because we preserve user
oids, but regnamespace isn't afaict.  I don't think it's extremely
likely that users store such reg* columns in tables, but we probably
still should fix this.

Greetings,

Andres Freund