21389 Host Metrics Temperature.Feature

The host_metrics source can now collect hardware temperature readings via a new temperature collector. When enabled, it emits temperature_celsius, temperature_max_celsius, and temperature_critical_celsius gauges, each tagged with the component label of the sensor it was read from.

The collector is opt-in: add temperature to the collectors list to enable it. Components that do not report a given value (for example a missing critical threshold) are skipped, and environments without temperature sensors simply produce no metrics.

authors: somaz94