[php-src] PR #23338: Fix wrong argument number in fsockopen/pfsockopen timeout error

Pull Request: https://github.com/php/php-src/pull/23338 Author: lacatoire php_fsockopen_stream() called zend_argument_value_error(6, ...) for the $timeout parameter, but $timeout is the **5th** argument. Because get_function_arg_name(func, arg_num) returns NULL when arg_num exceeds the actual argument count, the error message reported the wrong number and dropped the parameter name. Before: ``` ValueError: fsockopen(): Argument #6 must be -1 or between 0 and 4294967295 ``` After: ``` ValueError: fsockopen(): Argument #5 ($timeout) must be -1 or between 0 and 4294967295 ``` The same fix applies to pfsockopen(), which delegates to the same internal helper. A regression test is included; it does not require network connectivity since the ValueError is raised before any connection attempt.