Piggyback on new add_new_sstable_and_update_cache(), replacing
the previous add_sstables_and_update_cache().
Will be used by intra-node migration since we want it to be
safe when loading the cloned sstables. An unsplit sstable
can be cloned into destination which already ACKed split,
so we need this variant which splits sstable if needed,
while it's unsealed.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
3f8363300a