Add support for autoscaling/v2 API

[seleznev]

https://kubernetes.io/docs/reference/using-api/deprecation-guide/#horizontalpodautoscaler-v126:

The autoscaling/v2beta2 API version of HorizontalPodAutoscaler is no longer served as of v1.26.

• Migrate manifests and API clients to use the autoscaling/v2 API version, available since v1.23.

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Also I added urllib3 into requirements.txt because:

• We use it in tests directly.
• docker build broken because of 2.0.0a2 release:

  error: urllib3 2.0.0a2 is installed but urllib3<1.27,>=1.21.1 is required by {'requests'}
  

[halvaborsch]

LGTM