ROSA: rosaMachinePool for data plane

[enxebre]

/kind feature

Describe the solution you'd like
This introduces a common ground for collaboration on ROSA CAPA and basic ability to spin up a new cluster.

As a follow up we want to provide explore automated machine management for the data plane. For that we'll most likely want to have a new CAPA rosaMachinePool abstraction to consume the OCM machinePool API.

Anything else you would like to add:
[Miscellaneous information that will assist in solving the issue.]

Environment:

• Cluster-api-provider-aws version:
• Kubernetes version: (use kubectl version):
• OS (e.g. from /etc/os-release):

[k8s-ci-robot]

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