Allow caller to specify key CN in generate_attestation_from_EVP(). This is needed to generate attestations in the default Identity Credential HAL implementation which uses software KM. Test: atest VtsHalIdentityTargetTest Bug: 171745570 Change-Id: Ic96d1d2362851edca562c5defa1e48bdd0e6e060 Merged-In: I93b6cb939972c214dc67250dd62aa4fdd76273d6