Change SHA256 to Blake3 in KDF

[aniampio]

Recently we did some benchmark measurements on our implementation, and I noticed that SHA-256 was in one of the top ones. We use SHA256 in, for example, HKDF (every time we derive keys), so we might want to change it to Blake3 and see what it gives. We can't expect crazy changed overall, but it is still worth considering using Blake3 since it claims to be around 15 x faster than SHA-256 (https://github.com/BLAKE3-team/BLAKE3)