Remove resources if the provider is deleted

[ldx]

There are resources created by Kip during runtime:

• Instances for cells.
• Firewall rules or security groups.
• Cell CRDs.
• (Anything else?)

When a Kip instance is removed, the node will be removed soon by the control plane. However, all the VM instances, cell CRDs and SGs/firewalls that were active at that point will stay behind.

We need a way to detect when the Kip controller instance is gone, and remove all the resources it left.