Remove PQ TLS 1.2 Support

[alexw91]

Release Summary:

Removes draft support for post-quantum TLS 1.2 (draft-campagna-tls-bike-sike-hybrid) from s2n-tls. Support for post-quantum TLS 1.3 (draft-ietf-tls-hybrid-design) is kept.

Resolved issues:

None.

Description of changes:

Removes draft support for post-quantum TLS 1.2 (draft-campagna-tls-bike-sike-hybrid) from s2n-tls. Support for post-quantum TLS 1.3 (draft-ietf-tls-hybrid-design) is kept.

Call-outs:

1. Removes PQ TLS 1.2 support and the TLS_ECDHE_KYBER_RSA_WITH_AES_256_GCM_SHA384 cipher entirely from s2n-tls.
2. Older PQ TLS policies that should no longer be used have been deprecated.
3. s2n_ecdhe_kyber_rsa_with_aes_256_gcm_sha384 was removed from all cipher preference lists. If this removal made the cipher preference list identical to an already existing cipher preference list, then the entire cipher preference list was deleted and security policies migrated to use the other already existing cipher preference list. Otherwise, if no equivalent cipher preference list existed then s2n_ecdhe_kyber_rsa_with_aes_256_gcm_sha384 was removed in-place (eg for cipher_suites_pq_tls_1_0_2021_05_24).
4. All PQ TLS 1.2 tests have either been deleted or modified to support TLS 1.3, including Python and Rust bindings tests.
5. The function s2n_connection_get_kem_name() is kept, but now hardcoded to always return NONE in all circumstances so as to not break customers.

Testing:

• New unit tests were added to ensure that all PQ enabled Security Policies support TLS 1.3
• New unit tests were added to ensure that all deprecated security policies return S2N_ERR_DEPRECATED_SECURITY_POLICY when requested.
• All PQ TLS 1.2 tests have either been deleted or modified to support TLS 1.3, including Python and Rust bindings tests.

Remember:

• Any change to the library source code should at least include unit tests.
• Any change to the core stuffer or blob methods should include CBMC proofs.
• Any change to the CI or tests should:
  1. prove that the test succeeds for good input
  2. prove that the test fails for bad input (eg, a test for memory leaks fails when a memory leak is committed)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[alexw91]

Copy/Paste of kem_name function a few lines above, but with a call to s2n_connection_get_kem_group_name() instead of s2n_connection_get_kem_name().

[alexw91]

Moved "TLS 1.3 + PQ checks" further down in the function so that this code has access to the has_tls_13_cipher variable, so that a check that requires TLS 1.3 support for all PQ policies could be added.

[alexw91]

New unit tests for deprecated security policies.