hashMessage should have an optional parameter that can process hex like string

[script-money]

When I was using viem to generate signatures on the server side, I found that they were inconsistent with those generated in Solidity, causing the signatures to not be verified. After investigation, it was discovered that the length calculation for the string passed to hashMessage was different from that used in Solidity.

In ECDSA.sol,

    function toEthSignedMessageHash(bytes memory s) internal pure returns (bytes32) {
        return keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n", Strings.toString(s.length), s));
    }

In viem

export function hashMessage<TTo extends To = 'hex'>(
  message: string,
  to_?: TTo,
): HashMessage<TTo> {
  const messageBytes = stringToBytes(message)
  const prefixBytes = stringToBytes(
    `\x19Ethereum Signed Message:\n${messageBytes.length}`,
  )
  return keccak256(concat([prefixBytes, messageBytes]), to_)
}

If the string is in hex format and the lengths of strings toBytes(hexString).length and stringToBytes(hexString).length are not the same, this may result in the inability to generate the same signature with viem as in Solidity.

I found a commit 64a2f51 changed "toBytes" method to "stringToBytes" recently.

I suggest to add optional parameters to handle the hexstring with the original "toBytes" method to adapt to different situations.