chore: get kubeadm yaml rather than json

[rudoi]

What this PR does / why we need it:
Currently, the userdata has the kubeadm config structs as json, which kubeadm doesn't seem to like.

Sample from a provisioned host:

---
{"nodeRegistration":{"kubeletExtraArgs":{"cni-bin-dir":"/opt/cni/bin","cni-conf-dir":"/etc/cni/net.d","network-plugin":"cni","node-ip":"<redacted>"}},"localAPIEndpoint":{"advertiseAddress":"","bindPort":0}}

Special notes for your reviewer:

To avoid importing k/k I grabbed a utility function and copied it here, MarshalToYamlForCodecs.

Please confirm that if this PR changes any image versions, then that's the sole change this PR makes.

Release note:

[chuckha]

the json should be fine🤔 do you have the error that you got handy? Is it related to the APIEndpoint change where https:// is removed?

regardless yaml will be easier to debug for humans so I'm totally fine with this change.

[detiber]

That should be able to be parsed as valid yaml, but like @chuckha I also think this change is warranted for readability.

[rudoi]

@chuckha / @detiber wow uhhh y'all are right lol. I can't remember what error I hit but I can't seem to reproduce it. JSON works fine. Though I do agree the file looks nicer as YAML. Happy to change up anything if y'all want.

The https:// thing is a real issue though, I believe.

[chuckha]

/approve

Thanks @rudoi

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: chuckha, rudoi

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[detiber]

/lgtm