Use last PowerState instance in Statuses for power status

[DSakura207]

Description

This is for #15566. Now code will scan Statuses property and find last InstanceViewStatus, whose Code starts with PowerState.

Nuget package Microsoft.Azure.Management.Compute.Fluent has the class for the purpose, but it is being phased out so I didn't use that package.

Checklist

• I have read the Submitting Changes section of CONTRIBUTING.md
• The title of the PR is clear and informative
• The appropriate ChangeLog.md file(s) has been updated:
  • For any service, the ChangeLog.md file can be found at src/{{SERVICE}}/{{SERVICE}}/ChangeLog.md
  • A snippet outlining the change(s) made in the PR should be written under the ## Upcoming Release header -- no new version header should be added
• The PR does not introduce breaking changes
• If applicable, the changes made in the PR have proper test coverage
• For public API changes to cmdlets:
  • a cmdlet design review was approved for the changes in this repository (Microsoft internal only)
    • {Please put the link here}
  • the markdown help files have been regenerated using the commands listed here

[ghost]

Thank you for your contribution DSakura207! We will review the pull request and get back to you soon.

[wyunchi-ms]

/azp run azure-powershell - security-tools

[azure-pipelines]

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