standard error handling

[mhw0]

The current status of error handling is a bit mess, some functions return number value (length of data for instance) while some return status code.

I think we should standardize error handling for all the functions.

Suggestion:

enum eth_op {
  ETH_OK = 0,
  ETH_ERR_INVALID_ARGS = 1
}

enum eth_op eth_rlp_uint8(...) {
  if (args not looking ok) {
    return ETH_ERR_INVALID_ARGS;
  }

  ... do something
  return ETH_OK;
}

Breaks the compatibility, that's why it should be released in the major update.

[mhw0]

✅ RLP: 6c5946c