Invoke-RestMethod & Invoke-WebRequest: Add -HttpVersion parameter

[hayhay27]

Summary of the new document or enhancement

• List of articles that need to be updated:
  https://github.com/MicrosoftDocs/PowerShell-Docs/blob/staging/reference/7.2/Microsoft.PowerShell.Utility/Invoke-RestMethod.md
  https://github.com/MicrosoftDocs/PowerShell-Docs/blob/staging/reference/7.2/Microsoft.PowerShell.Utility/Invoke-WebRequest.md
• New articles that need to be created:
• Link(s) to related code PR(s) in the PowerShell/PowerShell repo:
  Add HttpVersion parameter to Invoke-WebRequest cmdlet PowerShell/PowerShell#15853
• Link(s) to related issue(s) in the PowerShell/PowerShell repo:
  invoke-restmethod does not support http/2 PowerShell/PowerShell#12641

Description of what changed

Added new parameter -HttpVersion that accepts http versions 1.0, 1.1, 2.0, 3.0