Using HorizontalPodAutoscaler v2

[matzew]

Fixes #6332

Proposed Changes

• Using HorizontalPodAutoscaler v2, since v2beta2 is being deprecated in k8s 1.23 (our next min-version)

Pre-review Checklist

• At least 80% unit test coverage
• E2E tests for any new behavior
• Docs PR for any user-facing impact
• Spec PR for any new API feature
• Conformance test for any change to the spec

Release Note

The HorizontalPodAutoscaler manifests have been updated to v2, which is available with k8s 1.23+

Docs

[matzew]

/hold
Holding for a few reasons:

• the v2 is not yet available on our current min-version, but will be soon (see discussion on Remove kind 1.22 testing, since we will min-version 1.23 soon #6548)
• The API is just "freshly" deprecated, and will be removed on the k8s 1.26.... so we still have some time to actually do this

[codecov]

Codecov Report

Base: 81.94% // Head: 81.94% // No change to project coverage 👍

Coverage data is based on head (0fd8361) compared to base (bd37622).
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6549   +/-   ##
=======================================
  Coverage   81.94%   81.94%           
=======================================
  Files         235      235           
  Lines       11738    11738           
=======================================
  Hits         9619     9619           
  Misses       1646     1646           
  Partials      473      473           

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[lionelvillard]

/lgtm
/approve

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lionelvillard, matzew

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[matzew]

/unhold