AS: Add error log print

[Xynnn007]

Before this commit, if error happens during serving the API, no explicit errors information will be printed on the terminal of AS.

With this patch, there will be an error log saying something like

[2024-11-15T09:41:59Z ERROR restful_as::restful] InternalError(
        Error {
            context: "attestation report evaluate",
            source: "Verifier evaluate failed: TDX Verifier: AA eventlog does not pass check. AAEL value : bb3dd9d0d81bcb0674b57992e6f8e8e3614fb6ce9006e7cf65c860bdea02db53df8e05b2d8479eae4fa8c8a06d5c4a88, Quote value 3f5b43108e554a781c46c3f47e6daf3de52e353358f032dc92add9b980ffdfb5e4861b7593d3d022538043c3fb72d431",
        },
    )

[fitzthum]

LGTM