cmd/swarm/swarm-smoke: sliding window test

[acud]

fixes #1095

example kubernetes deployment manifest:

smoke:
  image:
    repository: ethdevops/swarm
    tag: <tagg>
  schedule: "*/10 * * * *"
  config:
    swarmReplicas: 10
    operation: "sliding_window"
    extraFlags:
      - --sync-delay=60
      - --store=1500
      - --timeout=600
      - --single

[nonsense]

While I like the simplification of the wrap function, I am not sure this is the test when downloading all historical hashes that were uploaded.

[janos]

This is not a complete review. I still did not go through all changes.

[janos]

Additional comments to the first review.

[janos]

@justelad Thank you for addressing my comments and suggestions. LGTM.

[acud]

submitted upstream ethereum/go-ethereum#18967