use only public part to test key encapsulation

[petrovr]

Current oqs tests use one and the same context based on private key to test "encapsulate" and "decapsulate".

I would like to request encapsulate test to be based on key context based only on public part.

[baentsch]

Please point to the code/test locations you don't find right as well as the spec mandating different behaviour so we could treat this as a bug. Also welcome would be a PR fixing this suitably.

[petrovr]

It is related to #572.

Goal is to test de-serialisation and serialisation of public key as well.

---

In brief oqs_test_kems.c to use something closed to real use.

/* public context */
EVP_PKEY_get_octet_string_param(key, OSSL_PKEY_PARAM_PUB_KEY, ...
...
pubk = EVP_PKEY_new_raw_public_key_ex(...., KEMALG_NAME, ....);
...
ctx = EVP_PKEY_CTX_new_from_pkey(..., pubk, ...);
...
EVP_PKEY_encapsulate...(ctx, ...

/* private context */
ctx = EVP_PKEY_CTX_new_from_pkey(..., key, ...)
...
EVP_PKEY_decapsulate...(ctx, ...

[baentsch]

Understood. Would you be willing to contribute this via PR, @petrovr ?