⚠️ KCP tolerates diff not leading to changes on machines

[fabriziopandini]

What this PR does / why we need it:
As of today KCP perform a verbatin comparison between current and desired state of machines, and in case of diffs it triggers a rollout.

With this PR we are making the comparison smarter and ignore diff that are not leading to actual changes on machines.
e.g. files: [] or files: nill are different from a golang point of view, but they lead to the same cloud-init file on the machine, so KCP should not rollout in this case.

Please note that this change will also fix infinite rollouts that might be introduced when we drop the DefaulterRemoveUnknownOrOmitableFields from web hooks

Also, note that in a follow up iteration I would like to move tests currently implemented in the cloudinit package near to the new feature in kcp, but this is not in the critical path to unblock work on optional/required & last changed in webhook option.

/area provider/control-plane-kubeadm

Part of #10852

[mboersma]

Looks like an improvement that could lead to much less churn for KCP. 👍🏻

Could we spell "omittable" with two t's?

[fabriziopandini]

/test

[k8s-ci-robot]

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[fabriziopandini]

/test pull-cluster-api-e2e-conformance-ci-latest-main
/test pull-cluster-api-e2e-conformance-main
/test pull-cluster-api-e2e-latestk8s-main
/test pull-cluster-api-e2e-main
/test pull-cluster-api-e2e-mink8s-main
/test pull-cluster-api-e2e-upgrade-1-33-1-34-main

[sbueringer]

Thx!

/lgtm
/approve

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 814618a7ee855321e9cbe2b6aa4001ce7ab11d89

[k8s-ci-robot]

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