Configure providers in clusterctl.yaml to allow airgapped use

If these paths aren't configured, clusterctl will reach out to the GitHub release api https://github.com/kubernetes-sigs/cluster-api/releases and try to download the providers.

Technically you don't have to manually specify the versions like this if you've hard coded the versions: https://repo1.dsop.io/platform-one/distros/clusterapi/-/blob/master/vSphere/vsphere_clusterapi_bootstrap.sh#L822-826

It's also possible to specify the providers as ${CAPI_PROVIDERS}/cluster-api/latest/core-components.yaml with latest instead of the version. If you do that it will use the most recent version on disk if you don't specify versions with clusterctl init.