Add easy-to-run KATs to ML-KEM

[marsella]

There are a bunch of small modifications we need to make to ML-KEM to bring it up to our gold standard (see e.g. #135 #144 #145 #146 #147). ML-KEM currently can be run against the KATs (see kat.awk) if you download one of the rsp files and run it against the implementation. However, for faster iteration it would be nice to have a smaller Tests section with a few of the KATs hard-coded, so we can quickly load and :check-docstrings.

There are not official KATs for the final draft yet, but there are some candidate KATs available to test with.

• Reorganize ML-KEM directory to match the other directories we have (add Instantiations/ directory for ml_kem*.cry and a separate Tests/ directory -- see Common/EC/PrimeField/ for an example)
• Add a test file for each of the three instantiations. Put 2-3 KATs in each one. Make sure to use the final draft version. Add docs to cite the sources of the KATs.