Add a password discard confirmation

[Jookia]

This PR adds a confirmation dialog on password generator close that confirms discarding the password. Fixes #10831 .

Screenshots

Testing strategy

Tests are currently broken: Something about MessageBox::setNextAnswer is blocking the closing of the database in the test. Once this is fixed (I need help with this please) I will write tests that check:

• Closing can be aborted by clicking no
• Clicking yes always closes the dialog

Type of change

• ✅ New feature (change that adds functionality)