Avoid to convert the user parameter in specific case for show-if/hide-if macro

This is to add a really specific code in the UserTagHandler for the show-if/hide-if macro.

Related to https://github.com/xwikisas/application-confluence-migrator-pro/pull/235#discussion_r1871124195

In the old release of the confluence show-if/hide-if macro instead of having a specific parameter for the special value of the user, they used the user parameter to match by example all users with the value @authenticated. We need to avoid any transformation of this value, so we are able to map correctly the parameter in the macro converter.
Here are the parameter value that don't need to be transformed:

• @authenticated
• @anonymous
• @self

Note, if at some point another macro need some customisation like this, it would be good to provide in the converter a way to access to the raw parameter, and so we can manage this in a clean way.