Fix config-bootstrapper and test-runner RBAC

[upodroid]

/cc @dprotaso @kvmware

1st commit fixes the e2e serving errors @dprotaso mentioned
2nd commit fixes the config-bootstrapper errors. Basically, it was pointing to the old prow control plane cluster which I deleted this month.

Contents of the kubeconfig:

 REDACTED  C02CW0CDP3YY  ~  $  kg secret -n test-pods prow-kubeconfig -o yaml | yq '.data."kubeconfig.yaml"' | base64 -d | yq .contexts
- context:
    cluster: prow-build
    user: prow-build
  name: prow-build
- context:
    cluster: prow-trusted
    user: prow-trusted
  name: prow-trusted
- context:
    cluster: prow-control-plane
    user: prow-control-plane
  name: prow-control-plane

I'm working with sig-testing at Kubernetes on getting rid of the bearer tokens and using the gke auth plugins.

kubernetes/test-infra#28142

[knative-prow]

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[krsna-m]

You have some no newline issues else lgtm

[upodroid]

/hold

I had to revert my change earlier. Prow unfortunately doesn't understand different contexts properly. It assumes all users have cluster-admin which isn't good.

First order of business is extending config-bootstrapper to use a context.

[upodroid]

A quick fix would be to load a kubeconfig with just only the config-bootstrapper context.

[upodroid]

Also, it is 7 days till the release day so I don't really want to make some changes this week and cause testgrid to show extra flakes from infra changes/snafu

[upodroid]

/hold cancel

I created a dedicated secret for it with just a single context. I will experiment with the contexts after the release is done.

[krsna-m]

/lgtm