x-wing: Expose Encapsulate and Decapsulate traits from x-wing directly

[hoxxep]

Small usability PR. Using x-wing otherwise requires importing the kem crate directly (and syncing versions).

[newpavlov]

It's probably worth to re-export kem as well, i.e. to write pub use kem::{self, Decapsulate, Encapsulate};.

[hoxxep]

Very happy to add it in! What else are you aiming to expose in particular, or is this mostly for future-proofing?

If it's for exporting CryptoRng, perhaps it's also worth also exporting RngCore from kem to be able to (re)implement CryptoRng from a different version of rand? I can add that into this PR too if useful?

[newpavlov]

I think rand_core should be re-exported from kem, not from implementation crates.

[hoxxep]

Ah sorry – just realising traits is an entirely separate repo. Ignore the same PR comment.