upgrading, and deleting clusters.

For the 1.8 release, SIG Cluster Lifecycle continued to focus on expanding the
capabilities of kubeadm, which is both a user-facing tool to manage clusters
and a building block for higher-level provisioning systems. Starting
with the 1.8 release, kubeadm supports a new upgrade command and includes alpha
support for self hosting the cluster control plane.

- github.com/oklog/ulid: [v1.3.1](https://github.com/oklog/ulid/tree/v1.3.1)
- github.com/pascaldekloe/goe: [57f6aae](https://github.com/pascaldekloe/goe/tree/57f6aae)
- github.com/pelletier/go-toml: [v1.2.0](https://github.com/pelletier/go-toml/tree/v1.2.0)
- github.com/posener/complete: [v1.1.1](https://github.com/posener/complete/tree/v1.1.1)
- github.com/prometheus/tsdb: [v0.7.1](https://github.com/prometheus/tsdb/tree/v0.7.1)

- The `StructuredAuthenticationConfiguration` feature is now beta and enabled. ([#123719](https://github.com/kubernetes/kubernetes/pull/123719), [@enj](https://github.com/enj))
- The `kube_codegen` tool now ignores the vendor folder during code generation.
   ([#122729](https://github.com/kubernetes/kubernetes/pull/122729), [@jparrill](https://github.com/jparrill))