[gpu-op] Align Age column across all CRs #3210

The ClusterPolicy and NVIDIADriver CRs use type=string for the Age column. The GPUCluster CR uses type=date. We should use type=date for all CRs as that is consistent with built-in resources like Pods, Deployments, etc.

Below is sample output that shows the current Age column for all CRs.

# kubectl get clusterpolicy
NAME             STATUS   AGE
cluster-policy   ready    2026-10-26T18:21:00Z

# kubectl get nvd
NAME      STATUS   DEFAULT   AGE
default   ready    true      2026-11-06T03:30:01Z

# kubectl get gpucluster
NAME          STATUS   AGE
gpu-cluster   ready    7m26s

Fix: Change all CRs to type=date, then run make manifests and make sync-crds.
Done when: The CRDs are regenerated in config/crd/bases, deployments/gpu-operator/crds, and bundle/manifests, and kubectl get shows a relative age