auto-seal consensus private network

[unclezoro]

Describe the feature

The present auto seal consensus is limited to a solitary node.
The feature is to extend it to a private network. Like a single auto seal miner is active, with other full nodes able to synchronize through p2p network. This needs to

1. implement proper handler of NewBlock and NewBlockHashes which is almost empty now.
2. automatically manage the peers and decide to fetch/download block from the best peers.
3. a lightclient to verify and assemble the upcoming blocks; feeds to BeaconConsensusEngine.

Additional context

1. This could serve as a good example for broadening support to other networks like Polygon, BSC, which does not have any consensus client or op-node.
2. This feature also allows developer to verify the consistency of the Blockchain Executor by running a local cluster rather than syncing from an existed chain, thus preventing consensus uncertainty caused by certain bugs, such as mis-usage of 'map' in EVM.

Further

EIP225 Clique consensus protocol, Nethermind, Erigon, Go-ethereum, Open-Ethereum have implemented this Clique consensus engine, if reth could implement the same, it will improve the modularization of reth further and make things even simple for other EVM compatible chains.