slo-monitor: the pulling image time of the pod is incorrectly recorded as 1970-01-01 00:00:00 +0000 UTC

[zyuce]

What happened:
The slo-monitor collects pod lifecycle time by watching events, but it incorrectly records the time of starting pulling image.
I0122 02:27:28.157857 1 pod_monitor.go:324] Observed Pod default/netshoot creation: created 2024-01-22 02:27:21 +0000 UTC, pulling: 1970-01-01 00:00:00 +0000 UTC, pulled: 2024-01-22 02:27:26 +0000 UTC, running: 2024-01-22 02:27:28.157849816 +0000 UTC m=+1186.391220756

What you expected to happen:
The time of pulling image is recorded correctly.

How to reproduce it (as minimally and precisely as possible):
Deploy the slo-monitor in k8s cluster with --v=5, create a common pod.
And then observe the log like above.

[k8s-triage-robot]

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[k8s-triage-robot]

The Kubernetes project currently lacks enough active contributors to adequately respond to all issues.

This bot triages un-triaged issues according to the following rules:

• After 90d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
• After 30d of inactivity since lifecycle/rotten was applied, the issue is closed

You can:

• Mark this issue as fresh with /remove-lifecycle rotten
• Close this issue with /close
• Offer to help out with Issue Triage

Please send feedback to sig-contributor-experience at kubernetes/community.

/lifecycle rotten