add option for blockHash per EIP-1898

[macfarla]

Signed-off-by: Sally MacFarlane macfarla.github@gmail.com

Related - change status of EIP-1898 from stagnant to draft ethereum/EIPs#5980
Geth and Besu have both implemented support for this.

[Termina1]

Hi, its already used in production a lot, now it's very confusing to build any proxy/loadbalancing solution for RPC protocol. Let's merge it!

[macfarla]

Hi, its already used in production a lot, now it's very confusing to build any proxy/loadbalancing solution for RPC protocol. Let's merge it!

sounds good @Termina1 - how do we progress this PR?

[protolambda]

I support this change! eth_getProof to get hashes / roots should definitely support blockhash param. Geth implements this already too: https://github.com/ethereum/go-ethereum/blob/2189773093b2fe6d161b6477589f964470ff5bce/internal/ethapi/api.go#L658 and I think Nethermind has very flexible block/tag/number/object arguments for most RPCs too.

[lightclient]

I added a few tests to this PR for eth_getProof and eth_getBalance just to sanity check the change. speccheck is happy and the changes look good to me. Geth does already support the block hash in this position for all the methods addressed (I verified manually).

Thanks for the contribution!