[windows] Registry keys are not cleaned up after uninstall

[charlag]

Describe the bug
A clear and concise description of what the bug is.

To Reproduce
Steps to reproduce the behavior:

1. Install client
2. Settings->Desktop->Enable mailto handler
3. Uninstall client
4. Open regedit.exe
5. Check that HKEY_CURRENT_USER\SOFTWARE\CLASSES\tutanota.Mailto is still there

Expected behavior
Registry keys should be removed on uninstall

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: Windows 10, Windows 11
• Version 3.91.1

Additional context
This breaks Windows in certain scenarios, see #3787

Implementaion hints
We could potentially run the app during uninstall scrip with -u parameter to unregister keys easily. We should make sure we don't remove keys on app update.