Document configurable k0rdent CAPI providers

[nwneisen]

Document how MKE4 is configuring k0rdent CAPI providers.

https://github.com/MirantisContainers/mke/pull/475
https://github.com/MirantisContainers/mke-operator/pull/217

By default, the provider section is not output in the mke4.yaml output with mkectl init. When no providers are specified, MKE will only enable the sveltos provider because MKE4 depends on it. Once providers are specified, if sveltos is not one of them, it will be added.

The config to add providers to the MKE4 looks like

spec:
  providers:
    - name: k0smotron
    - name: cluster-api-provider-azure

Any valid k0rdent providers will work.

Note
Due to an issue with k0rdent that we are waiting on the next release to get a fix for, all providers are installed when the cluster is created. Once the cluster is up and running, the additional providers are disabled so they are not running.