Add support for post-quantum hybrid key exchange X25519Kyber768Draft00

[malhotrag]

X25519Kyber768Draft00 is supported by many browser vendors and CloudFlare. This support was added before X25519MLKEM768 was finalized. This PR adds support for detecting this key exchange group.

Please let me know if you want me to make any changes to this PR.

[rbsec]

Thanks for this - and sorry that it took me so long to get around to looking at it. I've been away, and it's been a busy few months.

[reneleonhardt]

Where can we check when this obsolete draft can be replaced by ML-KEM-512, ML-KEM-768 and ML-KEM-1024 (FIPS 203)?

bwesterb/draft-westerbaan-cfrg-hpke-xyber768d00@82d1b1a (Oct 23, 2024)

# Deprecrated

Kyber is obsoleted by ML-KEM.

Please use [X-Wing](https://github.com/dconnolly/draft-connolly-cfrg-xwing-kem) which combines X25519 and ML-KEM-768 for HPKE.

https://github.com/itzmeanjan/ml-kem