Include work items in groups direct transfer

When transfering a group that has group-level work items, these should be included in the list of migrated items.

This is done as part of the epic-to-work-item migration because the epics included in the group transfer will have an associated work item that needs to be present after the transfer.

Including work items in groups migrated using an export file will be handled in a separate issue: #446154 (comment 1841405294).