Support "dynamically sized" worker node pools with elemental nodes.

[atoy3731]

Describe the solution you'd like:
Currently when provisioning an RKE2/K3s cluster with Elemental, you statically define the sizes of your node pools, and when elemental machines that match labels come online, it will fill the size of that pool.

Specifically with pure worker pools (aka, when Controlplane and Etcd are not selected to avoid quorum issues), for situations where you dynamically want pools to grow as machines come online, it'd be useful to be able to select "Dynamically Sized" instead of a quantity of nodes. As new matching machines come online, they would automatically get added to that pool to scale it out without having to adjust the cluster configuration itself.

Anything else you would like to add:
N/A

Environment:

• Elemental release version (use cat /etc/os-release): 1.5.3
• Rancher version: 2.8.3
• Kubernetes version (use kubectl version): 1.2x+
• Cloud provider or hardware configuration: N/A

[kkaempf]

Not sure this can be handled within Elemental alone. This sounds more like a generic Rancher provisioning request 🤔

[atoy3731]

Not sure this can be handled within Elemental alone. This sounds more like a generic Rancher provisioning request 🤔

Yea, I wasn't sure what team this would fall under, but it is unique to Elemental provisioning through Rancher (since Elemental is the only provisioning mechanism that can dynamically machines to node pools as they come online). The other provisioning (like RKE2/K3s on AWS) is the opposite direction, where Rancher is actually triggering the creation of the machines.