New provider: aws-lc-rs

[jplock]

Would you be open to a pull request to add another provider that uses https://crates.io/crates/aws-lc-rs?

[franziskuskiefer]

Yeah, I'm open to adding other providers.

[jplock]

Adding this here for reference - rustls/rustls#1963

[cpu]

FWIW, I think building an aws-lc-rs backend in this repo might bump into the aws-lc-rs/ring HKDF API limitation I mentioned here. We worked around this in Rustls without much fuss because we had a separate HKDF-using-HMAC implementation where there was a convenient way to expose what we needed. Without that machinery at hand one might need to negotiate upstream changes or think of a different workaround.