Pull out hkdf and hmac modules as standalone crates

[jschneider-bensch]

This PR pulls out the libcrux::hkdf and libcrux::hmac modules, as well as their dependencies in the libcrux::hacl module into their own crates:

• libcrux-hkdf which only depends on sys/hacl and
• libcrux-hmac, which also depends on the new libcrux-hkdf crate

I've also replaced these modules in libcrux with a re-export of the standalone crates' APIs and pruned the libcrux::hacl module of the dead code.

[franziskuskiefer]

Thanks, looks good to me.
We should add the wycheproofs tests to the crates. But looks like they're not there yet. Can you file a follow up?

[jschneider-bensch]

Thanks, looks good to me. We should add the wycheproofs tests to the crates. But looks like they're not there yet. Can you file a follow up?

I've filed a follow up here: #306