SERVER-79160 changed movePrimary behavior for unsharded collections to preserve the UUID across shards. This was added because at that time tracked collections needed to preserve UUID after the move (so the sharding catalog would be consistent with the local catalog), all unsharded collections were going to be tracked and there were no moveCollection to move unsplittable collections. This had an unintended effect though explained by SERVER-87772, and considering for 8.0 we might have unsharded collections that are not tracked, we should restore the original movePrimary behavior.

As part of this ticket we should make sure we don't break compatibility with C2C.