Replace XML::Simple dependency

[ferki]

XML::Simple documentation states

The use of this module in new code is discouraged. Other modules are available which provide more straightforward and consistent interfaces. In particular, XML::LibXML is highly recommended.

Let's convert all XML-related code to XML::LibXML (which Rex already uses in Rex::Group::Lookup::XML).

[shadowcat-mst]

Also for "easier to use" it's worth considering XML::Twig or the standalone Mojo::DOM58