mvcc: partition_snapshot_row_cursor: Extract prepare_heap()
mvcc: partition_snapshot_row_cursor: Extract prepare_heap()

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