dcache consume api rework

[niki4smirn]

Before

adapter.consume_with_dcache(
    |msg, bytes| parse_payload(msg, bytes),
    |result, producers| match result {
        DCacheRead::Ok((msg, payload)) => {
            handle_message(msg, Some(payload), producers);
        }
        DCacheRead::NoRef(msg) | DCacheRead::Lost(msg) => {
            handle_message(msg, None, producers);
        }
        DCacheRead::SpedPast => {
            // What should I do with that?
        }
        DCacheRead::Empty => {}
    },
);

After

adapter.consume_with_dcache(
    |msg, bytes| parse_payload(msg, bytes),
    |msg, payload, producers| {
        handle_message(msg, payload, producers);
    },
);

tldr
DCacheRead::Empty => closure not called
DCacheRead::SpedPast => safe_assert, closure not called
DCacheRead::Lost => safe_assert, closure not called
DCacheRead::NoRef(msg) => payload is None
DCacheRead::Ok((msg, payload)) => payload is Some