Check if e2e upgrade tests should consider adding coredns and etcd upgrade

[chrischdi]

/kind feature

Describe the solution you'd like

Currently the upgrade tests for CAPV only consider upgrading the k8s parts.

In CAPI we also upgrade coredns and etcd (when the default version changes) using the variables ETCD_VERSION_UPGRADE_TO and COREDNS_VERSION_UPGRADE_TO.

Anything else you would like to add:

Maybe this already happens automatically, but we should check it and consider adding it if its not happening to stick to the combination tested on upstream kubernetes.

Environment:

[sbueringer]

Not sure if I understand the issue correctly.

As of now we don't set the env variables in CAPV upgrade tests. I think it's not strictly necessary as core CAPI already ensures we can upgrade to the correct etcd / CoreDNS versions.

If it's important for us that our CAPV e2e tests upgrade to the same versions tested by upstream then we should simply introduce it the same way as in core CAPI.
(Just a bit of additional work to ensure we configure this variables correctly, but we can copy that more or less from core CAPI)

[chrischdi]

Yeah, we've been unsure if we actually need this in CAPV, so more of a placeholder to not forget about it and think it through once.