tests/range_tombstone_list: add test for range_tombstone_accumulator
tests/range_tombstone_list: add test for range_tombstone_accumulator

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