Support consensus state in tendermint rpc

[zmanian]

I would like to be able to write consensus monitoring systems in rust.

The consensus_state endpoint can be very helpful for doing that.

This can be used to badger validators who aren't live yet.

[thanethomson]

@zmanian, do you want the RPC to automatically parse the vote strings and vote bit arrays returned by this endpoint?

[zmanian]

So I started to make something like this.

https://github.com/iqlusioninc/tm-launch-monitor/blob/main/main.go#L94-L122

This kind of tooling is sorely needed in the tendermint ecosystem.

Pulling apart the vote strings is a bit messy and I think it's why no standard blame tool has emerged.

I can see more usage for parsed vote strings than I can for the vote bit array.

[thanethomson]

Awesome, I've just added rudimentary support for the consensus_state endpoint in #719, but it just returns the vote strings and vote bit arrays in their string form. I'll work on parsing them tomorrow.

[thanethomson]

@zmanian, do you think the abstractions here would work for you for the vote strings?