fix: KWOK node GPU metrics not visible in RunAI UI

[eliranw]

Summary

• Fix KWOK virtual GPU node metrics not appearing in RunAI UI (GPU utilization, memory, free devices)
• The root cause: RunAI's dcgmMetricsRule recording rules join DCGM metrics with kube_pod_info on pod_ip to derive the node label. For the centralized KWOK exporter, this maps metrics to the system node where the pod runs, not to the virtual KWOK node.

Changes

• multi_node_exporter.go: Override the Hostname label with the actual KWOK node name (instead of a hash) so metrics can be correlated to the correct virtual node
• kwok-service.yaml (new): Dedicated Service for the KWOK exporter with component: status-exporter-kwok selector
• kwok-prometheusrule.yaml (new): PrometheusRule deployed to runai namespace that creates runai_dcgm_gpu_utilization, runai_dcgm_gpu_used_mebibytes, and runai_dcgm_gpu_total_mebibytes recording rules using Hostname directly as the node label, bypassing the kube_pod_info join
• service.yaml: Added component: status-exporter to selector to prevent the DaemonSet service from matching KWOK pods (avoids double-scraping)
• _helpers.tpl: Added component: status-exporter label to DaemonSet pod template

How it works

The PrometheusRule uses label_replace to set node from the Hostname label, then joins with runai_node_nodepool_excluded to add the nodepool label. Regular (non-KWOK) metrics have a hash-based Hostname that doesn't match any real node, so they are naturally filtered out by the join.

Test plan

• Deploy to test cluster with KWOK node
• Verify runai_dcgm_gpu_utilization, runai_dcgm_gpu_used_mebibytes, runai_dcgm_gpu_total_mebibytes show correct values for KWOK nodes in Prometheus
• Verify regular (non-KWOK) GPU node metrics are unaffected
• Verify no duplicate metrics from double-scraping
• Verify GPU type, Ready/total GPU devices, GPU memory visible in RunAI UI for KWOK nodes

[eliranw]

Clean, well-documented fix. The approach of creating parallel PrometheusRules with direct Hostname-to-node mapping is a good solution for the KWOK centralized exporter scenario. A few minor observations below.