Return an array instead of string to test memleak

The CURLOPT_PREREQFUNCTION leak test returned a constant string value.
Under opcache optimization, SCCP/constant folding may turn this into
an interned string, which is process-lifetime allocated and therefore
does not reliably trigger leak detection.

Use a dynamically allocated array containing random_bytes() instead.
This guarantees a non-interned, refcounted return value that exercises
the missing zval_ptr_dtor() path consistently under leak analyzers.

Author: Sjord

ext/curl/tests/curl_setopt_CURLOPT_PREREQFUNCTION.phpt

@@ -77,7 +77,7 @@ try {
 
 echo "\nTesting with invalid type\n";
 curl_setopt($ch, CURLOPT_PREREQFUNCTION, function() use ($port) {
-	return str_repeat('this should be an integer', 20);
+	return ['this should be an integer' => random_bytes(64)];
 });
 try {
     curl_exec($ch);