After T244492 we can remove the multiple column pagination from PreliminaryCheckService, since it will be handled by IndexPager.
We can define the multiple index fields in PreliminaryCheckPager::getIndexField, after which we can stop overriding IndexPager::doQuery, and instead override IndexPager::getQueryInfo and IndexPager::preprocessResults.
In doing this, we will also remove the virtual column lu_name_wiki, which currently causes errors when using Special:Investigate without CentralAuth enabled.