Add `lskv_cluster.py` for easily managing docker clusters

[jeffa5]

This changes the benchmarks to run lskv in containers compared to raw built objects.

It should also scale better to distributed testing since we now have the logic to do some governance things.

[github-actions[bot]]

Plots from benchmarking at ad5e4289e5d4b707bc392464b575727b80084228

Available from here

etcd/ecdf-latency_ms-None-nodes-vars.jpg

etcd/scatter-start_ms-latency_ms-None-nodes-vars.jpg

etcd/throughput_bar-rate-None-nodes-vars.jpg

k6/ecdf-latency_ms-None-nodes-vars.jpg

k6/scatter-start_ms-latency_ms-None-nodes-vars.jpg

perf/ecdf-latency_ms-http_version-nodes-vars.jpg

perf/scatter-start_ms-latency_ms-http_version-nodes-vars.jpg

ycsb/ecdf-latency_ms-nodes-operation-vars.jpg

ycsb/scatter-start_ms-latency_ms-nodes-operation-vars.jpg

ycsb/throughput_bar-rate-nodes-operation-vars.jpg