Automatic merge from submit-queue (batch tested with PRs 41297, 42638, 42666, 43039, 42567)
Allow minion floating IPs to be optional
**What this PR does / why we need it**:
Makes the generation of floating IPs for worker nodes optional, based on an env var. To quote the original issue:
> Currently, the OpenStack installation method assigns a floating IP to every single worker node. While this is fine for smaller clusters with a good sized IP pool, it can cause issues in environments with high node counts or less IPs available.
**Which issue this PR fixes**:
https://github.com/kubernetes/kubernetes/issues/40737
**Special notes for your reviewer**:
I used the conditions section of the Heat spec: https://docs.openstack.org/developer/heat/template_guide/hot_spec.html#conditions-section
**Release note**:
```release-note
OpenStack clusters can now specify whether worker nodes are assigned a floating IP
```
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