dutyGroup dimension missing from coordinator metrics

[forzamehlano]

as per https://github.com/opstree/druid-exporter/issues/9, it doesn't appear as though we're passing through the dutyGroup dimension from the coordinator metrics (https://druid.apache.org/docs/latest/operations/metrics.html#coordination) coordinator/global/time

This metric is necessary in properly understanding the performance of the coordinator and what it's spending its time doing during its cycle. Currently we have to also emit metrics to the log file to see this information.

[stale[bot]]

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