Avoid overflow in zend_list_insert

[OttoHollmann]

As described in https://bugs.php.net/bug.php?id=81399 declaring index as int may lead to overflow and later in segfault. Let's declare it as zend_long, because function zend_hash_index_add_new accepts zend_ulong.

[nikic]

As mentioned on the bug report, changing the type only here is not sufficient, because the ID stored in the resource structure will still get truncated. For PHP 8.1, we have switched the resource ID to zend_long, so the problem is properly resolved there. For older versions, we now error when overflowing the integer space.