Change the NuGet feed to use the governed powershell feed

[daxian-dbw]

PR Summary

Change the NuGet feed to use the governed PowerShell feed. This is a security requirement from Microsoft.
The function Update-CFSFeed is added to helper.psm1. Whenever we update the NuGet package, we need to run this function on an MS employee's dev machine to update the PowerShell feed.

PR Checklist

• PR has a meaningful title
  • Use the present tense and imperative mood when describing your changes
• Summarized changes
• Make sure you've added one or more new tests
• Make sure you've tested these changes in terminals that PowerShell is commonly used in (i.e. conhost.exe, Windows Terminal, Visual Studio Code Integrated Terminal, etc.)
• User-facing changes
  • Not Applicable
  • OR
  • Documentation needed at PowerShell-Docs
    • Doc Issue filed:

Microsoft Reviewers: Open in CodeFlow