Improve RemoteMachine provisioning

[makhov]

We need to improve the RemoteMachine SSH provisioner to make it more reliable and self-healing.

Things to keep in mind:

• k0s binary might be present on the machine already, no need to download it again
• At some point, we want to add existing k0s controller and worker nodes to the CAPI cluster without re-provisioning.

[apedriza]

@makhov Im taking a look at this issue. For the first item:

k0s binary might be present on the machine already, no need to download it again

Bootstrapconfig resource already have preInstalledK0s field so user has the possibility to avoid install k0s binary if it is present. It is OK that solution for you or have something else in mind?

about second item:

At some point, we want to add existing k0s controller and worker nodes to the CAPI cluster without re-provisioning.

what exactly do you mean with re-provisioning? I have been trying to add remote worker machines after an initial apply and it is working fine