feat: label NodeClaim termination and lifetime histograms with instance and capacity type

[pfernandes21]

Summary

The GPU Spot Availability dashboard's interruption panels (instance termination time, end-to-end termination, spot node lifetime before interruption) could only follow $cloud via a nodepool join — the underlying histograms had no instance-type dimension. This stamps the launched instance/capacity type on every histogram recorded when a NodeClaim is torn down so those panels can honor $instance_type / $gpu_type directly.

 karpenter_nodeclaims_instance_termination_duration_seconds{nodepool, cause}
+karpenter_nodeclaims_instance_termination_duration_seconds{nodepool, instance_type, capacity_type, cause}
 karpenter_nodeclaims_termination_duration_seconds{nodepool, cause}
+karpenter_nodeclaims_termination_duration_seconds{nodepool, instance_type, capacity_type, cause}
 karpenter_nodeclaims_lifetime_seconds{nodepool, capacity_type, origin, cause}
+karpenter_nodeclaims_lifetime_seconds{nodepool, instance_type, capacity_type, origin, cause}

Values come from the labels the cloud provider stamps on the NodeClaim at launch (node.kubernetes.io/instance-type, karpenter.sh/capacity-type), read via a shared terminationLabels(nodeClaim) in the lifecycle controller. A NodeClaim deleted before it launched (failed launch, registration timeout) reports unknown instead of an empty label — this also changes lifetime_seconds{capacity_type=""} to capacity_type="unknown" for that case. Cardinality is bounded by the instance types a NodePool can actually launch, as with the existing karpenter_nodeclaims_terminated_total labels.

Tests: the cloud_interrupted termination test now asserts the launched instance/capacity type on all three histograms, and a new case covers the never-launched → unknown path. go test ./pkg/controllers/nodeclaim/lifecycle/ -race passes against envtest 1.36.

Follow-up in the monorepo once merged: repin infra/kraftsman/fork, bump exa-scale, and switch the dashboard's interruption/lifetime panels from the nodepool→cloud join to direct instance_type=~"$instance_type" matchers.

Link to Devin session: https://app.devin.ai/sessions/78f39945389b48c8b60f35de366cb138
Open in Devin Desktop: https://app.devin.ai/desktop/session/78f39945389b48c8b60f35de366cb138?variant=devin
Requested by: @pfernandes21

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