Compute CREATE address without RLP library

[chfast]

We want to decouple RLP library (mostly used in testing infrastructure and MPT hashing) from the core EVM state modifications. The CREATE address derivation is the only place where RLP is used. For this we only need to implement RLP encoding for uint64.

See the TODO comment at https://github.com/ethereum/evmone/blob/v0.11.0/test/state/host.cpp#L149.

[AbhinavMir]

Hi @chfast ! Does the draft PR above look right? I looked at how Aleth used to encode JSON objects and bounced off from there to create a rlp_encode_uint64 function.