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/plugins/modifiercompiler.upper.php

@@ -0,0 +1,28 @@
+<?php
+/**
+ * Smarty plugin
+ *
+ * @package    Smarty
+ * @subpackage PluginsModifierCompiler
+ */
+/**
+ * Smarty upper modifier plugin
+ * Type:     modifier
+ * Name:     lower
+ * Purpose:  convert string to uppercase
+ *
+ * @link   https://www.smarty.net/manual/en/language.modifier.upper.php lower (Smarty online manual)
+ * @author Uwe Tews
+ *
+ * @param array $params parameters
+ *
+ * @return string with compiled code
+ */
+function smarty_modifiercompiler_upper($params)
+{
+    if (Smarty::$_MBSTRING) {
+        return 'mb_strtoupper(' . $params[ 0 ] . ', \'' . addslashes(Smarty::$_CHARSET) . '\')';
+    }
+    // no MBString fallback
+    return 'strtoupper(' . $params[ 0 ] . ')';
+}