Add staged split-role test

[brandond]

• Follow-up to Provisioning cluster with split role stuck at status updating #11645

We need to add a split-role test that mimics rancher's order of operations when joining nodes to the cluster

For split-role clusters, rancher waits for all etcd-only nodes to start containerd, kubelet, and etcd. It then joins the control-plane nodes to the cluster, and waits for them to start containerd, kubelet, and apiserver. Once that is done it joins the agents.

Our current tests just start all the nodes at once and rely on everything to come up eventually - which it does if you start them all at once.