Add a data-search-scope for wiki selection for user/groups suggestion widget

Currently, the user/group widgets only supports setting the user scope for the current wiki. It would be useful to also add the option to set a data-search-scope to allow the user to select from which wiki the data is retrieved. Also, similarly to XWIKI-22850: Add an option in a macro parameter to select the page/space for attachment suggestions, it would be nice to give the user an option in the macro UI to dynamically modify the search scope for the user/group selector.