use informers for pod events instead of Listing

[hakuna-matatah]

What type of PR is this?

Add one of the following kinds:
/kind bug

Optionally add one or more of the following kinds if applicable:
/kind failing-test

What this PR does / why we need it:

It's a quick fix to help calculate pod_startup_latencies effectively for large clusters and not worry about running into Apiserver side ttl issues nor worry about events being expired after 1h for larger clusters.

Which issue(s) this PR fixes:

Fixes #

It fixes these issues

• Pod startup latency calculation phases are not efficient and may result in error for larger clusters in ClusterLoader2 #2176
• Pod startup time phases are inaccurate in longer tests. #2006

Special notes for your reviewer:

[linux-foundation-easycla]

• ❌ The commit (769ce60). This user is missing the User's ID, preventing the EasyCLA check. Consult GitHub Help to resolve.For further assistance with EasyCLA, please submit a support request ticket.

[k8s-ci-robot]

@hakuna-matatah: PR needs rebase.

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[k8s-ci-robot]

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[k8s-ci-robot]

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: hakuna-matatah
Once this PR has been reviewed and has the lgtm label, please assign mborsz for approval by writing /assign @mborsz in a comment. For more information see the Kubernetes Code Review Process.

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Needs approval from an approver in each of these files:

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[hakuna-matatah]

/easycla