Prevent simple user from being able to set the hidden metadata for pages

Context: see https://forum.xwiki.org/t/only-offer-the-ability-to-hide-pages-to-advanced-users/13952

Right now, when editing a page, simple users see that there's the option of setting the page as hidden, and they may be confused about what it means and start using it in the wrong way. It also makes the UI more complex than it could be for simple users (the default).

The idea is to show the ability to set hidden pages to advanced users only, both in WYSIWYG standalone edit mode or in in-place edit mode (in the info tab of the docextra area).

Possible option to be discussed: Also hide the ability to set "view hidden pages" from the user profile when the user is simple.