add e2e test for epp metrics

[delavet]

This PR is related to #915 and adds an e2e test case to verify whether the epp exposes the correct metrics after traffic is generated.
This e2e test actually revealed an issue: currently the normalized_time_per_output_token_seconds metric is not being recorded correctly. However, to maintain the atomicity of this PR, I have left a TODO and will consider submitting a new issue to track the problem I discovered.

[k8s-ci-robot]

Hi @delavet. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[danehans]

/ok-to-test

[danehans]

@delavet great job with this PR. Fix the linter issue and all should be good.

/lgtm

[delavet]

Sorry for these linter issues. They have been resolved, please help check this again @danehans

[kfswain]

This looks great! Sorry its sat for so long
/lgtm

normalized_time_per_output_token_seconds metric is not being recorded correctly. However, to maintain the atomicity of this PR, I have left a TODO and will consider submitting a new issue to track the problem I discovered.

Do we have an issue created yet? This would be great to track

[kfswain]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: delavet, kfswain

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[delavet]

This looks great! Sorry its sat for so long /lgtm

normalized_time_per_output_token_seconds metric is not being recorded correctly. However, to maintain the atomicity of this PR, I have left a TODO and will consider submitting a new issue to track the problem I discovered.

Do we have an issue created yet? This would be great to track

Yes! this is the issue tracking it #939 .