Cardano Updates

All three rules fire only when the known type information uniquely
determines the outcome:

  ? - Duration : ?  ->  Timestamp - Duration : Timestamp
    Only Timestamp - Duration exists with Duration on the Sub rhs.
    Enables: \x -> x - 1s  (infer x : Timestamp)

  ? + ? : Duration  ->  Duration + Duration : Duration
    Only Duration + Duration produces Duration.
    Enables: \x -> \y -> m [now; now : x + y]  (infer both : Duration)

  ? - ? : Timestamp  ->  Timestamp - Duration : Timestamp
    Only Timestamp - Duration produces Timestamp via Sub.
    Enables: \x -> \y -> m [x - y; x]  (infer x : Timestamp, y : Duration)

Ordering: A (? - Duration) before C (? - ? : Timestamp) so the more
specific rhsTy=Duration match takes priority. B (? + ? : Duration)
after the existing Duration + Duration : ? rule so the known-both-sides
case is tried first.

- Use Text.unlines in prettyRelevanceArray and forHuman ContextDump
- Rename JSON keys eventsPerSecond and catchUpRatio to camelCase
- Simplify printArray to build a single Text value
- Use maybe [] Map.toList instead of Map.toList . fromMaybe Map.empty