Support for dynamic attester committee

[pompon0]

It will support collecting votes for a single batch for now. I've extended the rpc to support both pushing and pulling the votes (with dynamic committee we cannot really collect future votes). I've reworked the API to concentrate the api surface in one place.

I've also moved the rpc registry from rust code to protobuf enum to make enforcing compatibility easier.

I'll prepare a corresponding PR in zksync-era before merging to make sure that the integration is smooth e2e.

[brunoffranca]

Couple of notes:

1. If possible, I would prefer to have the attester code into its own actor. Otherwise it will be harder to understand. I also don't want the network actor to keep growing in size until it basically encapsulates all the code.
2. We can have yet another trait (Client) to be implemented on era. But we already have 3 (PayloadManager, PersistentBatchStore, PersistentBlockStore) and I want us to merge all these traits into one. The consensus repo really should have a single interface to interact with era. This will be better discussed on the offsite, but just keep in mind that you might not want to create more traits like this.

[aakoshh]

Big change!

It got me confused that all the persistence side and the querying of the batch store for the next thing to attest for is gone, and the PR description doesn't mention it at all. I suspect the reason is that you want to only call wait_for_qc() from zksync-era and push all the code over to that side which retrieves the data from the DB and saves the result.

It's true that some of the methods were (apart from maintaining metrics) merely passing the data through, and it looks like we just want to take care of the gossiping of the data now, and forget the interface described here, but one could also argue that so far the interface on the zksync-era side was relatively simple: implement the persistent store, start the runners, and you're done, now there will have to be more interaction about which method to call to update, which method to poll for changes, etc. Is there some general guideline in you mind about where to implement stuff when we have a choice? I guess we can discuss more on the offsite too.

[RomanBrodetski]

Some preliminary comments - diving deeper to the actual logic now

[aakoshh]

Nice one 👍