ext/standard: Reject NUL bytes in dl()

[LamentXU123]

Similar to #21942 and #21871. The dl function in std extension now silently truncates from NUL bytes. That is

 <?php
 $payload = "a\0/bcdefgh";
 set_error_handler(function ($severity, $message) {
      echo "warning: $message\n";
      return true;
  });
 try {
     var_dump(dl($payload));
 } catch (ValueError $e) {
     echo "ValueError: ", $e->getMessage(), "\n";
 }

Will return:

warning: dl(): Unable to load dynamic library 'a'

not

warning: dl(): Unable to load dynamic library 'a/bcdefgh'

Reproduce here

This PR rejects parameters containing NUL bytes as we always do in other cases.