multishard_combining_reader: shard_reader::remote_reader extract fill-buffer logic into do_fill_buffer()
multishard_combining_reader: shard_reader::remote_reader extract fill-buffer logic into do_fill_buffer()

avikivity/scylla,avikivity/scylla,avikivity/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla