fix: scale up broken for providers not implementing NodeGroup.GetOptions()

[apricote]

What type of PR is this?

/kind bug
/kind documentation

What this PR does / why we need it:

Properly handle calls to NodeGroup.GetOptions() that return cloudprovider.ErrNotImplemented in the scale up path.

Which issue(s) this PR fixes:

Fixes #6676

Special notes for your reviewer:

All call sites check for options != nil right after the error check.

Does this PR introduce a user-facing change?

Fixed scaling up node groups for Hetzner Provider

I have only confirmed that this was actually affecting the Hetzner Provider, there are other providers that also return ErrNotImplemented, but I did not verify if there was user visible breakage for them.

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[towca]

Thanks for reporting this!

I'm wondering if we could just change all of the cloud providers that return nil, cloudprovider.ErrNotImplemented to return nil, nil? That seems safer going forward, as the callers wouldn't have to remember to handle cloudprovider.ErrNotImplemented, and would preserve the semantics since returning nil options is supposed to fall back to the default options anyway.

@gjtempleton @MaciekPytel WDYT?

[towca]

@MaciekPytel volunteered for the long-term fix, merging this before that happens.

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: apricote, towca

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• cluster-autoscaler/OWNERS [towca]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment