Support spinning up a custom devnet with a single node based on 3SF

[syjn99]

Describe the feature

After merging #672, I think ream should be able to run a devnet in its own by using all the state transition functions and fork choice in 3sf-mini. By communicating via mpsc channel between services, I guess this work can also be a foundation for building P2P service (Related: #671). To achieve that, we need:

• A node MUST know the validator set of the network, which is fixed during the network lifecycle. Parse a YAML file that contains the list of validators.
• A node MUST know its duty for block proposing in round-robin manner.
• A node MUST vote for the view that it has.
• A node is NICE TO HAVE some API that can fetch the current head of the chain. Or we can naively return the full LeanState. -> I checked this item as done because Add RPC service for API to the lean node #684 manages it.

Additional context

No response

[syjn99]

https://x.com/ReamLabs/status/1953744042031992861

Most of the MUST tasks are now resolved, and the first item would be a separate issue after discussing at leanEthereum/leanSpec#8.