Fix: Refactored ContextMenu

[hishitetsu]

I don't think this will solve all problems, but I believe it is important to prevent further problems.

• Fixed problem with COM objects not being properly discarded on context menu warm-up
• Fixed problem where ThreadWithMesssageQueue was being used unnecessarily for shell extensions with no submenu. This will improve performance

Resolved / Related Issues

• Were these changes approved in an issue or discussion with the project maintainers? In order to prevent extra work, feature requests and changes to the codebase must be approved before the pull request will be reviewed. This prevents extra work for the contributors and maintainers.
  Closes #issue...

Validation
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