More typed interface for `RingBuffer` (and others)

[danielocfb]

RingBuffer (and Map) objects are not the easiest to use. One request we had come up more than once now is that it may prove beneficial to user acceptance to have the ring buffer take care of some of the nitty gritty byte copying and decoding itself, instead of forcing users to worry about it.

[anakryiko]

This might make sense as some sort of "add-on" on top of RingBuffer, but in most general case RingBuffer is just sending raw bytes, and each message can be of different size and type.

[hodgesds]

I had a poor attempt at generating serde in this branch for skeleton generated objects. There were some type conversions that I don't remember off the top of my head that I ran into. However, what I found worked somewhat well was using plain to handle skel generated types that were being passed over the ring buffer (example).

[hodgesds]

I think I remember now, serde doesn't work well with #[repr(C)] structs which libbpf-rs generates. This is a somewhat similar issue.