Upgrade from Smarty 3 to Smarty 4 to be PHP 8.1 compatible

Remove all Smarty4 dedicated tests, all are done in the same test file
like before

www/lib/smarty-4.1.0/libs/sysplugins/smartyexception.php

@@ -0,0 +1,19 @@
+<?php
+
+/**
+ * Smarty exception class
+ *
+ * @package Smarty
+ */
+class SmartyException extends Exception
+{
+    public static $escape = false;
+
+    /**
+     * @return string
+     */
+    public function __toString()
+    {
+        return ' --> Smarty: ' . (self::$escape ? htmlentities($this->message) : $this->message) . ' <-- ';
+    }
+}