repair: Add get_full_row_hashes_sink_op
repair: Add get_full_row_hashes_sink_op

It is a helper that works on the sink() of the get_full_row_hashes
rpc stream verb.

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