Cache: md5 replaced with xxHash

Author: dg

src/Caching/Cache.php

@@ -393,7 +393,7 @@ public function start($key): ?OutputHelper
 	 */
 	protected function generateKey($key): string
 	{
-		return $this->namespace . md5(is_scalar($key) ? (string) $key : serialize($key));
+		return $this->namespace . hash('xxh128', is_scalar($key) ? (string) $key : serialize($key));
 	}