Kubeadm: Add support for `kubeadm config print-defaults --api-objects {componentConfig}`

[fabriziopandini]

kubeadm config print-defaults command lets user to get a defaulted config file.

The command supports a --api-objects flag that allows to filter the api objects that will be included in the output. Currently value supported by this flag are only InitConfiguration, ClusterConfiguration and JoinConfiguration.

Since in v1.12 component config were moved out from ClusterConfiguration, now the --api-objects flag should be modified in order to accept also component config api objects: KubeletConfiguration and KubeProxyConfiguration

[Klaven]

I will take this issue.

[Klaven]

/lifecycle active

[Klaven]

@fabriziopandini Quick question, I saw some TODO's in the code that is related to this ticket. do you all want me to include the todo's in the PR?

An example of this would be found here: https://github.com/kubernetes/kubernetes/blob/e9a3aaa44b0655e0ca67be6d460a4ef0774e0648/cmd/kubeadm/app/cmd/config.go#L175

Anyhow. I'm still working on this, just wanted to know if you all would like me to clean up the TODO's that are in the code I'm working with.
thanks

[fabriziopandini]

@Klaven
The two changes are un-related, even if impacting the same source file, so IMO it will be better to make a separated PR

[Klaven]

This ticket looks to be working on current master. @fabriziopandini can confirm. ticket should be closed.

[fabriziopandini]

/close
many many thanks to @Klaven for help on investigating this ticket

[k8s-ci-robot]

@fabriziopandini: Closing this issue.

In response to this:

/close
many many thanks to @Klaven for help on investigating this ticket

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