[2] Support pre-created floating IPs in openstack

[viktor-f]

Proposed feature

Currently if I want to use floating IPs for the nodes created by terraform in openstack, then terraform will create a new floating IP for each node. Then when removing a node terraform will also remove the floating IP. I want to be able to use pre-created floating IPs when creating nodes in openstack projects with terraform. So I can specify a specific floating IP that already exists and terraform will attach it to the new node. When deleting the node terraform should unattach the floating IP but keep it in the project instead of deleting it. The purpose is so that we can have a stable set of IPs when recreating nodes.

This should be managed as a new option when adding a new node. Similar to how we currently can chose to create nodes with or without floating IPs. It should be possible to have a cluster where some nodes use pre-created floating IPs and some do not.

This should be implemented on our kubespray fork. But we should try to upstream the change.

Proposed alternatives

No response

Additional context

No response

Definition of done

• [ ] New option when creating a node to specify an existing floating IP to attach instead of creating a new one.
• [ ] Keep the floating IP when deleting a node
• [ ] Try to upstream the changes after merging it to our fork