Function delegate_call_slice_res 

pub fn delegate_call_slice_res<const DATA_CAP: usize>(
    contract: [u8; 20],
    calldata: &[u8],
    gas: u64,
    offset: usize,
) -> Result<(usize, [u8; DATA_CAP]), (usize, [u8; DATA_CAP])>

Same as the other slice function, returning Result depending on return or revert.