feat: primary implementation of the protocol

[olegfomenko]

What?

This PR brings in primary implementation part for the consensus and library overall.

[cylewitruk]

Looks good in general -- left a few minor comments.

If the message contents aren't going to be changing then I would much prefer to see a binary serialization instead of serde_json which is notoriously slow and results in much larger payloads. Can recommend protobuf, speedy and rkyv, or even manual serialization if the messages are fixed.

Just for general info I do have some serialization benchmarking here (code here) for some stacks-core stuff, if that helps with some inspiration.