Add Cluster API provider and addon extensions

[kukacz]

Feature Request

Describe the feature you'd like:
Cluster API core structures were built into KCL module recently as #147 . To improve the practical usability of the module it would be nice to also add KCL modules implementing infrastructure provider and add-on APIs. Those are necessary to define objects for deployment on common public clouds, on metal3 infra or deployment of Helm charts on top of managed clusters.

• https://github.com/kubernetes-sigs/cluster-api-provider-aws
• https://github.com/kubernetes-sigs/cluster-api-provider-azure
• https://github.com/kubernetes-sigs/cluster-api-addon-provider-helm
• https://github.com/kubernetes-sigs/cluster-api-provider-gcp
• https://github.com/metal3-io/cluster-api-provider-metal3