Initialize policy files for coco attestation verifier

[ssolit]

The coco attestation verifier uses a policy system, where a map of (policy_name, policy_rego) is initialized, and then verification requests are handled with a policy specified. E.g. for sharing the root key requests, the enclave-server would ask its CoCo verifier to verify with the share_root policy. These policies were previously initialized in test cases, but should instead be initialized by the server itself at launch.