OCM-7149 | feat: adjust review comments from pre release

[gdbranco]

• Adjusts documentation over aws_subnets_ids
• Adjusts defaults for account roles to match expectation for HCP clusters
• Adjusts listening method from default ingress to supply external/internal depending on cluster being private or not

[openshift-ci[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ciaranRoche, gdbranco

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