Feature: Add update functionality for Kubernetes cluster

[raz-bn]

What problem are you facing?

I want to be able to update my K8s cluster managed by the do provider.
add/remove/update node pools, upgrade k8s version, add/remove tags, etc. are all supported my the godo sdk.
https://pkg.go.dev/github.com/digitalocean/godo#KubernetesService

[ADustyOldMuffin]

Hey thanks for this! Making issues for the updates was next on my list!