PQCKAT: Differences from NIST’s reference KAT

[quannguyen247]

I noticed that the KATs in this repo differ from the ones available on the NIST PQC main page.
It seems that the NIST site still hosts the older KATs, so for clarity and reproducibility, we should:

• add a copy of the original (old) KATs that match exactly what NIST published,
• keep the current (fixed) PQCKAT as default,
• document explicitly which set corresponds to which version (NIST’s original vs fixed).
  This would help users verify compliance when testing against either the official NIST submission package or the corrected reference implementation :D