Update help content for TabCompletion tests only if it does not exist

[adityapatwardhan]

PR Summary

The TabCompletion tests need help content to be present. Currently we update the help in user scope if it does not exists. The help content could be in all users scope and would be found by tab completion.

The change also checks for help content in All Users scope.

PR Checklist

• PR has a meaningful title
  • Use the present tense and imperative mood when describing your changes
• Summarized changes
• Change is not breaking
• 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: to the beginning of the title and remove the prefix when the PR is ready.
• User-facing changes
  • Not Applicable
  • OR
  • User-facing Documentation needed
    • Issue filed - Issue link:
• Testing - New and feature
  • Not Applicable 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
    • Add [feature] if the change is significant or affects feature tests

[adityapatwardhan]

@JamesWTruher Pushed a change. Please have a look.

[JamesWTruher]

lgtm