Support Optimism

[varasev]

There are a few things which could be implemented in OpenEthereum to support working with Optimism. The additional features are based on the features for TheMerge, so it could be implemented after we implement TheMerge.

Example of the changes for Geth: ethereum-optimism/reference-optimistic-geth#11

At a high level the patchset includes:

• a change to the engine api to pass in transactions that aren’t from the mempool, used for L1 to L2 txs
• a new tx type for L1 to L2 txs
• handling deposits of ETH in the state transition function
• don’t accept the new tx type in the mempool

Overview of Optimism: https://github.com/ethereum-optimism/optimistic-specs/blob/main/specs/overview.md (especially, Engine API changes)