add relative standard deviation to aggregated test execution metrics

[OVI3D0]

Description

Adds relative standard deviation to aggregated test result metrics. Users can now see the spread of their OSB test results. (RSD is currently only calculated for the mean)

Example:

   {
    "task": "wait-until-merges-finish",
    "operation": "wait-until-merges-finish",
    "throughput": {
     "min": 74.41136845553248,
     "mean": 74.41136845553248,
     "median": 74.41136845553248,
     "max": 74.41136845553248,
     "unit": "ops/s",
     "mean_rsd": 5.7260883182218825
    },
    "latency": {
     "100_0": 12.996128527447581,
     "mean": 12.996128527447581,
     "unit": "ms",
     "mean_rsd": 5.875897232448762
    },
    "service_time": {
     "100_0": 12.996128527447581,
     "mean": 12.996128527447581,
     "unit": "ms",
     "mean_rsd": 5.875897232448762
    },
    "client_processing_time": {
     "100_0": 0.6900834268890321,
     "mean": 0.6900834268890321,
     "unit": "ms",
     "mean_rsd": 1.172341871616217
    },
    "processing_time": {
     "100_0": 13.791589008178562,
     "mean": 13.791589008178562,
     "unit": "ms",
     "mean_rsd": 5.595395107897675
    },
    "error_rate": 0.0,
    "error_rate_rsd": 0,
    "duration": 3.3562859753146768,
    "duration_rsd": 1.6848600926145232
   },

Issues Resolved

662

Testing

• [x] New functionality includes testing

make test

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[OVI3D0]

You may want to change the 100_0 to max in the results summary, either in this or a future check-in.

Should this be done for regular test executions as well? 100_0 is used across regular test executions as well. Example:

    "latency": {
     "50_0": 206.59688568115234,
     "100_0": 235.18186950683594,
     "mean": 203.5783863067627,
     "unit": "ms"
    },