feat(lownodeutilization): expose node classification metrics

[tiraboschi]

Description

Expose classification metrics to track and observe node utilization and decisions:

• descheduler_lownodeutilization_node_utilization_threshold: threshold values (0-1)
• descheduler_lownodeutilization_node_utilization_value: actual utilization (0-1)
• descheduler_lownodeutilization_node_classification: classification result (0/1/2)
• descheduler_lownodeutilization_threshold_mode: static vs deviation-based (0/1)

All utilization metrics use 0-1 ratio format for consistency with Prometheus best practices and easy comparison in queries.

Checklist

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• PR Description: Is the PR description clear, providing enough context and explaining the motivation for the change?
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[k8s-ci-robot]

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[k8s-ci-robot]

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