Add robust generate command to show all optional fields

When running `eksctl anywhere generate clusterconfig`, the default doesn't include all the fields that can be configured as mentioned in the documentation. Adding an option to show all the optional fields that can be filled in, like a template, will make it easier to show what are all the fields that can be configured.

Start at the eksctl anywhere generate clusterconfig command and compare its current output with the documented configurable fields. Define how an option for a complete template should behave, then verify that the generated configuration exposes all optional fields described in the documentation.

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