🐛 Make print-policy consistent with print-cloudformation-template

[dlipovetsky]

What type of PR is this?
/kind bug

What this PR does / why we need it:
Previously, print-policy claimed to output all policies, but in fact it missed some policies, because it did not use the code as print-cloudformation-template. This change makes print-policy use the same code, making it consistent.

Also, print-policy would not output valid JSON, but rather multiple, concatenated JSON documents. It now outputs all policies as a valid JSON object, where the keys are policy names, and the values are the policies.

Before:

> clusterawsadm bootstrap iam print-policy
AWSIAMManagedPolicyControllers {
...
}
AWSIAMManagedPolicyControllersEKS {
...
}
AWSIAMManagedPolicyCloudProviderControlPlane {
...
}

After

{
  "AWSIAMManagedPolicyCloudProviderControlPlane": {
...
  },
  "AWSIAMManagedPolicyCloudProviderNodes": {
...
  },
  "AWSIAMManagedPolicyControllers": {
...
  }
}

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #4339

Special notes for your reviewer:

Checklist:

• squashed commits
• includes documentation
• includes emoji in title
• adds unit tests
• adds or updates e2e tests

Release note:

The clusterawsadm print-policy command now prints all the policies in the template generated by the print-cloudformation-template command, and when it outputs multiple policies, the output is valid JSON. 

[richardcase]

/lgtm
/approve

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: a5af1864f6082590300bf012e69e0bd2007906ce

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: richardcase

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[dlipovetsky]

/cherrypick release-2.9 release-2.8

[k8s-infra-cherrypick-robot]

@dlipovetsky: new pull request created: #5658

In response to this:

/cherrypick release-2.9 release-2.8

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[dlipovetsky]

/cherrypick release-2.8

[k8s-infra-cherrypick-robot]

@dlipovetsky: new pull request created: #5659

In response to this:

/cherrypick release-2.8

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.