New-AzSshKey should log to Warning stream instead of console

[PalmEmanuel]

Description

New-AzSshKey should log to a stream that PowerShell understands, and not the console. The stream chosen in this PR is to change it to the Warning stream to be consistent with how the Az CLI outputs the same information.

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 PalmEmanuel! We will review the pull request and get back to you soon.

[ghost]

All CLA requirements met.

[wyunchi-ms]

Please resolve the conflicts.

[wyunchi-ms]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[wyunchi-ms]

/azp run azure-powershell - security-tools

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).