Chain-prometheus-exporter: Expand to monitor timeouts

[Thahara]

We would like to monitor the amount of timeouts per validator in each epoch, this data is available from chain via concordium-client:

concordium-client --grpc-ip grpc.mainnet.concordium.software --secure raw GetWinningValidatorsEpoch --epoch 9265 --genesis-index 5 | jq '[.[] | select(.present == false)] | group_by(.winner) | map({winner: .[0].winner, count: length})'

[
  {
    "winner": 507,
    "count": 1
  },
  {
    "winner": 1484,
    "count": 4
  },
  .
  .
  .
  {
    "winner": 95363,
    "count": 10
  },
  {
    "winner": 95364,
    "count": 6
  }
]

Where "winner" is the validator id, and "count" is the number of times that validator timed out on baking a block in the epoch. So "winner" should be a label on the metric, and "count" should be the metric.
For the sake of convenience, it could also be nice to add a second metric of the epoch, with a label of the protocolVersion, that is available from the concordium-client:

concordium-client --grpc-ip grpc.mainnet.concordium.software --secure raw GetConsensusInfo