Need tuple support for ABI library

[trinhdn2]

The future universal IPaymaster contract interface will be decribed as below:

interface IPaymaster {
    function validateAndPayForPaymasterTransaction(
        bytes32 _txHash,
        Transaction calldata _transaction
    ) external payable returns (bytes4 magic, bytes memory context);

    function postTransaction(
        bytes calldata _context,
        Transaction calldata _transaction,
        bytes32 _txHash,
        ExecutionResult _txResult,
        uint256 _maxRefundedGas
    ) external payable;
}

The validateAndPayForPaymasterTransaction will be called first by core blockchain during the transaction processing, in order to determine if this transaction can be sponsored gas or not. It's output is a tuple (bytes4 magic, bytes memory context), and there isn't any method to properly unpack this bytes slice result. It throws unsupported arg type: tuple error.

Currently the outdated ABI library of tomochain only supports these types. We need an official and unified method to handle tuple packing/unpacking.