[Elastic Agent] Agent metrics visualizations use wrong minimum interval causing erroneous viz

**Version:** 8.15.1
**Issue:** Elastic Agent monitoring data is collected by default every 60 Seconds...
BUT in the visualizations the `@timestamp` histogram is set to minimum interval to `seconds` which is to granular, thus creates additional buckets with missing information causes the visualization to be very erroneously displayed.


**Fix:** The correct minimum interval should be set at the data collection rate ... i.e. 1 minute... then everything works fine ... BTW should also drop partial buckets.