Add responses for necessary attributes from the mock pkcs11 module

For the mock pkcs11 module to be helpful for testing with other tools (pkcs11-tool, openssh, ...) it is needed to provide RSA modulus, exponent (mandatory for PKCS#11, the merged option CKA_PUBLIC_KEY_INFO is not standard afaik), providing class and a subject are also good idea, though not mandatory.

The public key parts are exported from the public key in the hardcoded certificate.