insufficient privilege with pg_read_all_stats granted

[Costa Alexoglou <costa@xxxxxxxxxx>]

Hey folks,

I run PostgreSQL v15.8 (docker official image), and there is an issue when reading pg_stat_staments table with a result of query most of the times having `<insufficient privilege>` value.

I have created the user that I use to fetch the data with the following way:
```
CREATE USER abcd WITH NOSUPERUSER NOCREATEROLE NOINHERIT LOGIN;

GRANT pg_read_all_stats, pg_stat_scan_tables, pg_read_all_settings to abcd;

GRANT pg_monitor to abcd;

```

I explicitly gave `pg_read_all_stats` and also called `pg_monitor` just to be on the safe side, but stil I get the insufficient privilege error.

```

SELECT
   r.rolname AS member,
   m.rolname AS role
FROM
   pg_auth_members am
JOIN
   pg_roles r ON r.oid = am.member
JOIN
   pg_roles m ON m.oid = am.roleid
WHERE
   m.rolname = 'pg_read_all_stats'
   AND r.rolname = 'abcd';

 member |       role
--------+-------------------
 abcd   | pg_read_all_stats
(1 row)

```

I also tried with PostgreSQL v14.13, and this was not the case, it was working fine as expected.
Then I tried v16.4 and v17beta3, and I faced the <insufficient privilege> issue, so I guess something changed v15 onwards?