add system insights to analysis report

[qjiang002]

Add system insights to analysis report

Natural-language insights of the results are generated from an api. Here is an example.

[
    {"SalientFeatureStat":"As the value of span_density increases, the system performance will increase. System developers can consider improving the performance of samples with smaller span_density value."},
    {"SalientFeatureStat":"As the value of span_length increases, the system performance will decrease. System developers can consider improving the performance of samples with larger span_length value."},
    {"SalientFeatureStat":"As the value of span_econ increases, the system performance will increase. System developers can consider improving the performance of samples with smaller span_econ value."},
    {"SalientFeatureStat":"As the value of span_efre increases, the system performance will increase. System developers can consider improving the performance of samples with smaller span_efre value."},
    {"MaxPerformanceGapFeatureStat":"The maximum and minimum performance difference of the system on the span_true_label feature's bucket is the largest of all the features."},
    {"FrequentMispredictionStat":"The system frequently mispredicted samples with label `O` as `MISC`, the percentage of errors accounted for 0.14754098360655737 of the total."},
    {"FrequentMispredictionStat":"The system frequently mispredicted samples with label `ORG` as `O`, the percentage of errors accounted for 0.12786885245901639 of the total."},
    {"FrequentMispredictionStat":"The system frequently mispredicted samples with label `O` as `ORG`, the percentage of errors accounted for 0.1180327868852459 of the total."}
]

Now they can be displayed in the analysis report. The System Insights section is only displayed when the API returns non-empty results.