Proof of concept Eth-flavor RPC (Metamask) compatibility

[lrettig]

Goal: it should be possible to see an account balance, submit a simple tx, and see tx status using Metamask via Eth-flavor JSON-RPC API.

Resources:

• https://github.com/filecoin-project/lotus/blob/master/chain/types/ethtypes/eth_transactions.go#L152-L193
• https://github.com/harmony-one/harmony/pull/3495
• https://github.com/harmony-one/docs-developer/blob/9232844cb6fc75d68ab42069c433d29305f8b6fb/developers/api/README.md
• https://ethereum.github.io/execution-apis/api-documentation/
• https://ethereum.org/en/developers/docs/apis/json-rpc/#json-rpc-methods
• https://docs.taraxa.io/develop/taraxa-rpc-specs

[lrettig]

Closing in favor of #277, will continue investigation there