Fix tooltip for variable expansion and include description

[jborean93]

PR Summary

Fixes the tooltip for non-scoped variables to include the type and variable name like it does for scoped variables. Also includes the variable description if present on the variable object.

PR Context

It looks like there is a bug where the tooltip was built for a variable but not included in the completion result, this PR makes sure that isn't thrown away.

It also makes a further change to include the variable description if it's present. This may not be used for user variables but there are a few builtin variables where is a description and would be nice to include in the tooltip.

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
  • Experimental feature(s) needed
    • Experimental feature name(s):
• 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 opened an issue in the relevant tool repository. This may include:
    • Impact on PowerShell Editor Services which is used in the PowerShell extension for VSCode
      (which runs in a different PS Host).
      • Issue filed:
    • Impact on Completions (both in the console and in editors) - one of PowerShell's most powerful features.
      • Issue filed:
    • Impact on PSScriptAnalyzer (which provides linting & formatting in the editor extensions).
      • Issue filed:
    • Impact on EditorSyntax (which provides syntax highlighting with in VSCode, GitHub, and many other editors).
      • Issue filed:

[iSazonov]

LGTM with 2 style comment.

(Since it is very small PR you can add descriptions to some system variables where absent if you want.)

[JustinGrote]

Updated PSES PR so that this will work if merged.

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[jborean93]

Thanks for the review and merge.

[JustinGrote]

Thank you @iSazonov !