VPA: Per-node recommendations (very early draft)

[bboreham]

What type of PR is this?

/kind feature

/kind api-change

What this PR does / why we need it:

This is a very early draft in pursuit of AEP-7942.

Adds an optional field scope on the VPA object, to let the VPA components generate and update more fine-grained recommendations.

Only one value of scope is implemented by this PR: node.
If this is set, record the node name as an extra label on each pod, then extract it when writing the recommendation.
Inside the admission-controller we recognize which node the pod will run on by unpacking nodeAffinity.

Special notes for your reviewer:

The change to version.go is intended as temporary while testing, not intended to be merged.

Does this PR introduce a user-facing change?

Adds an optional field `scope` on the VPA object, to let the VPA components generate and update more fine-grained recommendations. See AEP-7942.

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

AEP-7942

[k8s-ci-robot]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[voelzmo]

@bboreham Thanks for starting this! Can you give me a ping once this is in a state where you think it is mostly doing what it should do?

[voelzmo]

For future reference: with the current state, the VPA status gets a scope string for each containerRecommendation, resulting in a structure like this

conditions:
  - lastTransitionTime: "2025-03-26T12:35:08Z"
    status: "True"
    type: RecommendationProvided
recommendation:
  containerRecommendations:
    - containerName: pause
      lowerBound:
        cpu: 100m
        memory: 262144k
      scope: node=kind-control-plane
      target:
        cpu: 100m
        memory: 262144k
      uncappedTarget:
        cpu: 25m
        memory: 262144k
      upperBound:
        cpu: 185m
        memory: 262144k

So for clusters with a big number of nodes the status grows quite a lot.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: bboreham
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[k8s-ci-robot]

PR needs rebase.

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