Refactor metrics management with AbstractMetricsManager

[kirktrue]

Introduces AbstractMetricsManager to centralize sensor and metric creation, reducing code duplication across metrics manager classes. Refactors FetchMetricsManager, ShareFetchMetricsManager, and all metrics manager classes to extend AbstractMetricsManager and use newSensorBuilder and newMetricName helpers. Updates SensorBuilder to support more flexible metric and sensor creation. This change improves maintainability and consistency in metrics handling.

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