Expose consensus critical metrics directly from gpbft

[masih]

This repo provides f3 observe command to dump all messages exchanged as part of F3. One then would need to query them to answer questions like:

• Who is currently participating?
• What percentage of power is participating?

This is fine but not ideal. Because, gpbft already has all of this information along with the cache of all the validated messages. For alerting purposes alone it would be useful not to force operators to run an observer to get these metrics.

[Kubuxu]

I'm not sure if the metrics I've added are good enough for it. They are useful for debugging and quick looks, but in most scenarios, they will cap out at 66% because we will move on when a quorum is reached.