airshipctl and clusterctl integration

[alanmeadows]

Problem description (if applicable)
For both ephemeral and target invokations of airshipctl cluster initinfra as well as a non-existent pivot command we intend to integrate the clusterctl pkg as a library.

While the clusterctl pkg continues to develop, this issue represents the effort of beginning that integration to understand the specific gaps remaining, especially the work we need to accomplish upstream within clusterctl.

Proposed change
For the airshipctl cluster initinfra commands, leverage the clusterctl library to perform the init, effectively equivalent to a clusterctl init. This will initially be equivalent to a kubectl apply of the provider resources, and we will build on the gaps remaining for leveraging metal3-io as a provider to just providing that - for instance, ensuring that the baremetal-operator, ironic, and so on are also instantiated, as well as BareMetalHost records to support subsequent Machine provisioning.

Within airshipctl, there is a need to be able to feed provider resources to a library like clusterctl. There has been work done upstream in clusterctl to support pulling provider resources from a local file system. We need to understand whether this will work for the way airshipctl renders documents through Kustomize and emits them as Document objects as part of a bundle - see the following pull request in clusterctl. Will we create a fake filesystem and provide that to clusterctl or enhance it upstream to support a YAML byte stream?

Potential impacts
There may be requirements for clusterctl upstream that may need to be solved locally in airshipctl.

[jezogwza]

Already there are separate issue closed or in progress for integrating clusterctl init and clusterctl move.