refactor: replace kubectl operation with k8s apiclient call

[allencloud]

Signed-off-by: Allen Sun [email protected]

Describe what this PR does / why we need it

1. remove several const values which are never used: RemoteApplyYaml, RemoteCmdGetNetworkInterface, RemoteCmdExistNetworkInterface;
2. Use built-in package k8s.Client when executing kubectl command, like kubectl delete node xxx, kubectl get nodes; After this pull request, there are still some kubectl command there, like kubectl drain and kubectl uncordon in upgrade operation. I found that k8s.Client has not contained drain and uncordon command, and we should use another kubernetes/kubectl package to cover the above both.
3. rename function isHostName into isHostInExistingCluster to be more readable.
4. flatten the struct runtime.Runtime to avoid useless embedding.

Does this pull request fix one issue?

none

Describe how you did it

none

Describe how to verify it

none

Special notes for reviews

[justadogistaken]

Feel confused about the KubeadmConfigFromClusterfile. I notice that "*kubeadm.KubeadmConfig" above is used to setup the final cluster, but what is KubeadmConfigFromClusterfile capable of?

[allencloud]

I think it is because that we lack the design of how many ways we allow to input KubeadmConfig to a cluster instance. If the sealer policy allows to input KubeadmConfig from Clusterfile, then KubeadmConfigFromClusterfile is useful.

I wish to make it strictly enough when we are evolving, otherwise it may be out of control. Still be design problem, I think. @justadogistaken