🐛 Define subnetID when creating ovn LB member

[nikParasyr]

What this PR does / why we need it:
Define subnetID on ovn LB member creation when the user is using different networks for the cluster and the loadbalancer

Which issue(s) this PR fixes:
Fixes #2790

Special notes for your reviewer:
In general I have some concerns with the approach, would like input from your side:

1. I'm using openStackCluster.Status.APIServerLoadBalancer.LoadBalancerNetwork.ID. While working on this i noticed that the field is not always populated ( related PR )
2. I'm checking whether the provider is "ovn", amphora also supports different subnet IDs (although i've never seen it in action). I could drop this check but it would require point 1 being resolved ( in theory we could always set subnetID on member create opts == openStackCluster.Status.Network.Subnets[0].ID -- see point 3 )
3. The subnetID is set to openStackCluster.Status.Network.Subnets[0].ID. A control-plane machine can be attached to different subnets ( if OSM.spec.ports. are defined ). I couldnt find a way to get the subnetID from the spec though as a user can define just a spec.ports[0].network.id (or a filter) and OSM.status doesn't provide info on subnetID. So the assumption is that the control-plane machine is using the cluster subnet.

TODOs:

• squashed commits
• if necessary:
  • includes documentation
  • adds unit tests

/hold

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[k8s-ci-robot]

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[k8s-ci-robot]

Hi @nikParasyr. Thanks for your PR.

I'm waiting for a github.com member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[lentzi90]

/ok-to-test

[nikParasyr]

/retest