Add HPKE support

[072i]

Problem:

Add HPKE support. It seems that aws-lc-sys has already generated bindings for HPKE-related functions, such as EVP_HPKE_CTX_setup_sender, but you don’t recommend relying on it directly. Therefore, I’d like to have an HPKE wrapper, similar to the CryptoKit API.

Solution:

I could try to create my own wrapper, but why is it not recommended to directly rely on aws-lc-sys?

[072i]

#300 (comment)