bundle: when forcing acceptance of incoming delta also accept snapshot Snapshot where never considered reusable and the unbundling side always tried to find a delta from them. In the `forced` mode this is counter-productive because it will either connect two delta-tree that should not be connected or it will spend potentially a lot of time because creating a full snapshot anyway. So in this mode, we accept the full snapshot as is. This changeset is benchmarked with its children so please do not split them apart when landing.