Support `Azure-selected zone (Preview)` for availability zones

[timja]

What feature do you want to see added?

See https://learn.microsoft.com/en-us/azure/virtual-machines/create-portal-availability-zone#restrictions

Need to test public IP behaviour, see:

• New Public IPs must be Zone Redundant or use an Azure-Selected Zone.
• Existing Public IPs aren't supported for an Azure-selected zone. They can be added after deployment.

ARM:
https://learn.microsoft.com/en-us/azure/templates/microsoft.compute/virtualmachines?pivots=deployment-language-bicep#placement

Specifically:

      "placement": {
        "zonePlacementPolicy": "Any"
      }

Also review scalesets with this

Upstream changes

No response

Are you interested in contributing this feature?

No response

[timja]

#704 mostly implements this but there's some sort of bug with the ARM API:

Public preview for 'placement' setting is not enabled in this region

Its enabled in basically all regions, (including what I tested in) and if I copy out the ARM template and deploy it with Azure CLI it works absolutely fine....

I've removed the UI selection from that PR for now.