PR Summary

Fix #11782

The ComEnumerator was introduced back in early .NET Core 2.0 preview period of time (#4553), because GetEnumerator() didn't work on COM object even if the object can be cast to IEnumerable and .NET Core team said it was by design at the time (dotnet/runtime#21690).
With .NET Core 3.1, GetEnumerator() works on the COM objects that can be cast to IEnumerable 🎉
So we can directly use the .NET Core support to get the enumerator for a COM object that implements IEnumerable.

However, for the COM object that can be cast to IEnumerator, exception is thrown when calling MoveNext() on it.
So we still need the ComEnumerator, but much simplified to just cover the case that the COM object implements COM.IEnumVARIANT interface.

PR Context

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 enumerated concerns in the summary. This may include:
    • Impact on PowerShell Editor Services which is used in the PowerShell extension for VSCode (which runs in a different PS Host).
    • Impact on Completions (both in the console and in editors) - one of PowerShell's most powerful features.
    • Impact on PSScriptAnalyzer (which provides linting & formatting in the editor extensions).
    • Impact on EditorSyntax (which provides syntax highlighting with in VSCode, GitHub, and many other editors).