Expose init_data to policy

[fitzthum]

Now that the init_data spec is merged, we should think about how we will evaluate the init data with Trustee.

Currently we don't really expose the init_data to either the attestation policy or the resource policy in the KBS. We had talked about extending the claims map of each verifier to include init_data, but that hasn't really happened. Maybe we should instead directly provide the init_data to opa engine in addition to the claims map? Should we do this for both the AA and KBS?