Gets the fields with calculation actions in the order their values are recalculated (CO, PDF 1.3); empty when absent.
public IReadOnlyList<PdfField> CalculationOrder { get; }
ISO 32000-2 §12.7.3, Table 224, and §12.6.3. An element that is not one of the form's fields is skipped with an
AcroFormEntryInvalid diagnostic. Calculations are not run.