Update the vertical scaling test to account for CPMSO

The etcd vertical scaling test manually creates a new machine to scale-up and then deletes it to scale-down.
This is effectively horizontally scaling the machines from 3->4->3.

With the ControlPlaneMachineSetOperator (CPMSO) present however, there is a race where once the test scales up to 4, the CPMSO will detect an excess of Ready machines and delete an older one to scale-down back to the desired control-plane size.
https://github.com/openshift/cluster-control-plane-machine-set-operator/blob/925943433d4c224465ae605e8eb6550926dc0dd4/pkg/controllers/controlplanemachineset/updates.go#L320-L345

This fails the vertical scaling test, and in particular blocks the following PR from landing:

https://github.com/openshift/cluster-control-plane-machine-set-operator/pull/98

The vertical scaling test should be updated to not horizontally scale, by serially scaling up then down, and instead initiate scaling by machine deletion so CPMSO can replace that machine with a new one.

The test would also have to detect whether CPMS is not present and in that case fall back to manually creating a new machine to replace the deleted one.

Prior discussion on slack:
https://coreos.slack.com/archives/C027U68LP/p1664320169916089