Support standard deviation and json output for job stats

In the job stats, in addition to the max, min and average,
it will also display the standard deviation.

A new option --json is added to the rdci to output the results
in json format.

In the job stats, using the GMT time instead of timestamp
for start and end time.

Change-Id: If245c4fc4854a1dc867f97ff5aa9112af7962eca


[ROCm/rdc commit: e6d910f67a]

projects/rdc/protos/rdc.proto

@@ -414,7 +414,7 @@ message JobStatsSummary {
   uint64 max_value = 1;
   uint64 min_value = 2;
   uint64 average = 3;
-
+  double standard_deviation = 4;
 }
 
 message GpuUsageInfo {