Consider reworking `ZydisShortString`

[athre0z]

Because #259 had to remove the struct packing on aarch64 darwin, it might be worth considering to do what @flobernd suggested in a response to the PR:

Maybe as an improvement, we could prepend the length to the actual strings (this should be easily possible as we generate the strings anyways) and remove the 'length' field from the struct. In this case a struct would not even be necessary, but probably still desired as a hint.