test: introduce a simple regression test using cassandra-stress
test: introduce a simple regression test using cassandra-stress

Test steps:
 1. Run a write workload
 2. Run a read workload (after the write - cache will contain some data)
 3. Restart node, run a read workload (cache will be empty)
 4. Run a mixed read write workload.

Signed-off-by: Amos Kong <eb01d8f828a6c9a20be4534e72e049aaf41503df@scylladb.com>

amoskong/scylla-cluster-tests,scylladb/scylla-cluster-tests,amoskong/scylla-cluster-tests,scylladb/scylla-cluster-tests,amoskong/scylla-cluster-tests,scylladb/scylla-longevity-tests,scylladb/scylla-longevity-tests,scylladb/scylla-cluster-tests,amoskong/scylla-cluster-tests,scylladb/scylla-longevity-tests,amoskong/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests