Update example files

[SWilson4]

This PR

• updates example_kem and example_sig to use ML-KEM and ML-DSA instead of Kyber and Dilithium
• adds example_sig_stfl to test_cmdline.py.

• Does this PR change the input/output behaviour of a cryptographic algorithm (i.e., does it change known answer test values)? (If so, a version bump will be required from x.y.z to x.(y+1).0.)
• Does this PR change the list of algorithms available -- either adding, removing, or renaming? Does this PR otherwise change an API? (If so, PRs in fully supported downstream projects dependent on these, i.e., oqs-provider will also need to be ready for review and merge by the time this is merged.)