VSCE: Uninstall survey for VS Code extension

Created by: jjinnii

Feature request description

Similar to the bext nps uninstall survey, we want to try and collect feedback on why users might uninstall the VSCE. While we already have CTAs for providing feedback, it's a valuable source of user feedback to ask why at uninstall.

Additional context

Can we use native VS Code notifications at uninstall with an nps survey?