Add aimed_for_deletion parameter to GroupsFinder

We need to add a way to filter for groups that have been marked for deletion.

Implementation Guide

1. Add a boolean aimed_for_deletion parameter to the GroupFinder.
   • When blank or nil, no additional filtering must be performed.
   • When true, filter for groups that are aimed for deletion.
   • When false, filter for groups that are not aimed for deletion.

See ProjectFinder and EE::ProjectsFinder for reference