Migrate from MessageDialog to ContentDialog

[michael-hawker]

Still using deprecated MessageDialog in a few places:

• Showing License
• Close Confirmation
• Save Error
• Unhandled Errors

[michael-hawker]

Also, the unhandled errors dialog has a button to go to feedback hub which should instead point here now. Ideally, we do something like VS Code does where it fills in some info about your version, the error, etc...