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/docs/designers/language-basic-syntax.md

@@ -0,0 +1,33 @@
+Basic Syntax
+============
+
+A simple Smarty template could look like this:
+```html
+<h1>{$title|escape}</h1>
+<ul>
+    {foreach $cities as $city}
+        <li>{$city.name|escape} ({$city.population})</li>
+    {foreachelse}
+        <li>no cities found</li>        
+    {/foreach}
+</ul>
+```
+
+All Smarty template tags are enclosed within delimiters. By default
+these are `{` and `}`, but they can be
+[changed](../programmers/api-variables/variable-left-delimiter.md).
+
+For the examples in this manual, we will assume that you are using the
+default delimiters. In Smarty, all content outside of delimiters is
+displayed as static content, or unchanged. When Smarty encounters
+template tags, it attempts to interpret them, and displays the
+appropriate output in their place.
+
+The basis components of the Smarty syntax are:
+- [Comments](./language-basic-syntax/language-syntax-comments.md)
+- [Variables](./language-basic-syntax/language-syntax-variables.md)
+- [Functions](./language-basic-syntax/language-syntax-functions.md)
+- [Attributes](./language-basic-syntax/language-syntax-attributes.md)
+- [Quotes](./language-basic-syntax/language-syntax-quotes.md)
+- [Math](./language-basic-syntax/language-math.md)
+- [Escaping](./language-basic-syntax/language-escaping.md)