[WIP] Add e2e test for HorizontalPodAutoscaler

[karlkfi]

We get a bunch of support tickets involving HPA and metrics-service. This test uses both, which should help us ensure this use case works going forward.

Current related known issues:

• metrics-service is a single replica, and when it fails or is rescheduled, API Discovery will error.
• HPA updates its status relatively frequently, which can sometimes trigger the fight detector.

This test likely won't trigger either of those issues on kind, but might on GKE, especially autopilot. If the test is flakey tho, we'll have more motivation to fix them.

[google-oss-prow]

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[google-oss-prow]

@karlkfi: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
kpt-config-sync-presubmit	d101c00	link	true	/test kpt-config-sync-presubmit

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