Adding Automatic Zone Placement

[audreyttt]

Description

Adding four new parameters to New-AzVmssConfig and Update-AzVmss, as requested in this design: https://github.com/Azure/azure-powershell-cmdlet-review-pr/issues/1510

Mandatory Checklist

• Please choose the target release of Azure PowerShell. (⚠️Target release is a different concept from API readiness. Please click below links for details.)

  • [x] General release
  • [ ] Public preview
  • [ ] Private preview
  • [ ] Engineering build
  • [ ] No need for a release

• [x] Check this box to confirm: I have read the Submitting Changes section of CONTRIBUTING.md and reviewed the following information:

• SHOULD update ChangeLog.md file(s) appropriately
  • Update src/{{SERVICE}}/{{SERVICE}}/ChangeLog.md.
    • A snippet outlining the change(s) made in the PR should be written under the ## Upcoming Release header in the past tense.
  • Should not change ChangeLog.md if no new release is required, such as fixing test case only.
• SHOULD regenerate markdown help files if there is cmdlet API change. Instruction
• SHOULD have proper test coverage for changes in pull request.
• SHOULD NOT adjust version of module manually in pull request

[azure-client-tools-bot-prd[bot]]

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