Introduce a lane_id_t/lane_t type

[eyalroz]

We have many functions returning lane ids or numbers-of-lanes. Mostly those use unsigned. But for better readability/clarity, I'm thinking of introducing something like:

using lane_id_t = unsigned;

within the kat namespace.

Users - if I have any that look at this issue, which is unlikely - are welcome to comment on this prospect.

[eyalroz]

One dilemma I have is that a lane_id_t doesn't quite sound like something you would put numbers of lanes in.