Type-stubs for `pg_fetch_all` are incorrect

[JoelNiemela]

The current type-stubs for pg_fetch_all are as follows:

/**
 * @return array<int, array>
 * @refcount 1
 */
#[\Since('8.1')]
function pg_fetch_all(\PgSql\Result $result, int $mode = PGSQL_ASSOC): array
{
}

(See https://github.com/phpstan/php-8-stubs/blob/1f23686dca88ed6d9a96c673d16ce11a16746af4/stubs/ext/pgsql/pg_fetch_all.php)

But as far as I can tell, pg_fetch_all actually returns list<array>. I've tried to verify this by looking through the pg_fetch_all source, and I'm quite sure it will always return a list, but it's a bit too dense for me to be certain.

I've also run the following assert on our codebase, and at least for all our queries, it true:

$data = pg_fetch_all($result);
assert(array_is_list($data));

Side-note: this is much less important, but would it in theory be possible to do something like the following, to further restrict the type?

/**
 * @return ($mode is PGSQL_NUM
 *     ? list<list<string|null>>
 *     : ($mode is PGSQL_ASSOC
 *         ? list<array<string, ?null>>
 *         : list<array<array-key, ?string>>
 *     )
 * )
 */