Work Items: Add workItems query to fetch all group/project work items that user has access to

Summary

Similar to issues query which supports fetching all the issues from projects that the user has visibility to, we need to create an equivalent workItems query that does the same. Currently, work items can only be fetched by Group or Project scope. This is needed for #238440 where users should be able to see everything assigned to them even at the group level, as well as in future once Issues are migrated to be Work Items.