Merge "identity: Clarify validity period for auth keys."

     *  - issuer: CN shall be set to "Android Identity Credential Key". (fixed value:

     *    same on all certs)

     *

     *  - validity: should be from current time and one year in the future (365 days).

     *  - validity: should be from current time and 31536000 seconds in the

     *    future (approximately 365 days).

     *

     *  - subjectPublicKeyInfo: must contain attested public key.

     *