ci update script: use release tags and add make targets

[prezha]

fixes: #9898

the update script now correctly picks up github releases' tags

also, added make targets as:
make update-kubernetes-version
to automatically update local repo with newest k8s versions (stable and latest), and:
make update-kubernetes-version-pr
to additionally automatically create pr

example output:

❯ make update-kubernetes-version 
(cd hack/update/kubernetes_version && \
 go run update_kubernetes_version.go)
I1210 01:24:49.534560    5453 update_kubernetes_version.go:140] Kubernetes versions: 'stable' is v1.20.0 and 'latest' is v1.20.1-rc.0
I1210 01:24:49.536565    5453 update.go:111] The Plan:
{
  "pkg/minikube/bootstrapper/bsutil/testdata/v1.20/containerd-api-port.yaml": {
    "replace": {
      "kubernetesVersion:.*": "kubernetesVersion: v1.20.0"
    }
  },
  "pkg/minikube/bootstrapper/bsutil/testdata/v1.20/containerd-pod-network-cidr.yaml": {
    "replace": {
      "kubernetesVersion:.*": "kubernetesVersion: v1.20.0"
    }
  },
  "pkg/minikube/bootstrapper/bsutil/testdata/v1.20/containerd.yaml": {
    "replace": {
      "kubernetesVersion:.*": "kubernetesVersion: v1.20.0"
    }
  },
  "pkg/minikube/bootstrapper/bsutil/testdata/v1.20/crio-options-gates.yaml": {
    "replace": {
      "kubernetesVersion:.*": "kubernetesVersion: v1.20.0"
    }
  },
  "pkg/minikube/bootstrapper/bsutil/testdata/v1.20/crio.yaml": {
    "replace": {
      "kubernetesVersion:.*": "kubernetesVersion: v1.20.0"
    }
  },
  "pkg/minikube/bootstrapper/bsutil/testdata/v1.20/default.yaml": {
    "replace": {
      "kubernetesVersion:.*": "kubernetesVersion: v1.20.0"
    }
  },
  "pkg/minikube/bootstrapper/bsutil/testdata/v1.20/dns.yaml": {
    "replace": {
      "kubernetesVersion:.*": "kubernetesVersion: v1.20.0"
    }
  },
  "pkg/minikube/bootstrapper/bsutil/testdata/v1.20/image-repository.yaml": {
    "replace": {
      "kubernetesVersion:.*": "kubernetesVersion: v1.20.0"
    }
  },
  "pkg/minikube/bootstrapper/bsutil/testdata/v1.20/options.yaml": {
    "replace": {
      "kubernetesVersion:.*": "kubernetesVersion: v1.20.0"
    }
  },
  "pkg/minikube/constants/constants.go": {
    "replace": {
      "DefaultKubernetesVersion = \".*": "DefaultKubernetesVersion = \"v1.20.0\"",
      "NewestKubernetesVersion = \".*": "NewestKubernetesVersion = \"v1.20.1-rc.0\""
    }
  },
  "site/content/en/docs/commands/start.md": {
    "replace": {
      "'latest' for .*\\)": "'latest' for v1.20.1-rc.0)",
      "'stable' for .*,": "'stable' for v1.20.0,"
    }
  }
}
I1210 01:24:49.541219    5453 update.go:120] Local repo successfully updated

note that the script already updates site/content/en/docs/commands/start.md, so we do not need to run make generate-docs additionally

[k8s-ci-robot]

Hi @prezha. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[minikube-bot]

Can one of the admins verify this patch?

[medyagh]

this will help with our automation significantly
thank you @prezha

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: medyagh, prezha

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