Function compute_report 

pub fn compute_report(
    baseline: &[Record],
    candidate: &[Record],
    pricing: &Pricing,
    seed: Option<u64>,
) -> DiffReport

Compute a DiffReport from a baseline and candidate trace.

The Judge axis is set to empty(Axis::Judge) because no Judge is supplied here; the Python layer plugs in a Judge via compute_report_with_judge.