rollout: Report health for all cases

[gvso]

This reports the health for all possible cases. In particular, it reports inconclusive diagnosis (no enough requests) and healthy diagnosis without enough elapsed time.

[gvso]

The two new reports look like:

rollout.cloud.run/lastHealthReport: |-
      status: healthy, but no enough time since last rollout
      metrics:
      - error-rate-percent: 0.00 (needs 1.00)
      - request-count: 5 (needs 0)
      lastUpdate: 2020-08-18T15:10:16-04:00
rollout.cloud.run/lastRollout: '2020-08-18T15:09:35-04:00'

rollout.cloud.run/lastHealthReport: |-
      status: inconclusive
      metrics:
      - request-count: 0 (needs 100)
      lastUpdate: 2020-08-18T15:35:00-04:00

[ahmetb]

🤔 it's sort of nice to omit other metrics in the status report when they're not relevant, but I suspect that might cause more confusion than it's helping. (e.g. people might think the metrics they configured aren't being taken into consideration by the program).

[gvso]

I had a dilemma between your point and the user not knowing what inconclusive means when the other criteria seems fine. Maybe we should do inconclusive, no enough requests?