`kafka_dae_diagnostics`: runstate readback

[Tom-Willemsen]

Proposed logic:

• If latest runInfo msg is a run stop
  • SETUP
• If latest runInfo msg is a run start
  • If we have received 'recent' frames on _event topic for this run:
    • If percentage of vetoed frames in buffer of last N frames >=50%
      • If 'most' of the recent vetoed frames are from runcontrol vetoes:
        • WAITING
      • Otherwise
        • VETOING
    • If percentage of vetoed frames in buffer of last N frames < 50%
      • RUNNING
  • If we have not received 'recent' frames on _event topic for this run:
    • PROCESSING?

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Pause/resume logic will also need adding after #39 - not yet clear how kdaectrl will notify consumers that a run is paused.

One option would be to make it a "paused veto" (hard veto which prevents events being emitted, but configured from software like runcontrol), which we could then treat in the same way as runcontrol from a consumer perspective.