Implement Group Policy settings for PSResource Repository

[adityapatwardhan]

PR Summary

Implement Group Policy settings for PSResource Repository.
Policy allows administrator to define an allow list for Uris that are allowed to be used for finding and installing resources.

The format for the policy is as follows:

Name=PSGallery;Uri=https://www.powershellgallery.com/api/v2/

PR Context

Fixes #1696

PR Checklist

• PR has a meaningful title
  • Use the present tense and imperative mood when describing your changes
• Summarized changes
• Make sure all .h, .cpp, .cs, .ps1 and .psm1 files have the correct copyright header
• This PR is ready to merge and is not Work in Progress.
  • If the PR is work in progress, please add the prefix WIP: or [ WIP ] to the beginning of the title (the WIP bot will keep its status check at Pending while the prefix is present) and remove the prefix when the PR is ready.
• Breaking changes
  • None
  • OR
  • Documentation needed
    • Issue filed: Add documentation for Group Policy Settings for PSResourceGet repositories MicrosoftDocs/PowerShell-Docs-PSGet#163
• User-facing changes
  • Not Applicable
  • OR
  • Documentation needed
    • Issue filed:
• Testing - New and feature
  • N/A or can only be tested interactively
  • OR
  • Make sure you've added a new test if existing tests do not effectively test the code changed
• Tooling
  • I have considered the user experience from a tooling perspective and don't believe tooling will be impacted.
  • OR
  • I have considered the user experience from a tooling perspective and enumerated concerns in the summary.