Make title of DetailedList on Windows more prominent

### What is the problem or limitation you are having?

On Windows and Qt, the title of DetailedList is in the same font as the sub title.

### Describe the solution you'd like

The title should be more prominent. It should be rendered using the default font face and size for the platform; the subtitle should use a font that is 20% smaller than the default font size.

### Describe alternatives you've considered

-

### Additional context

On other platforms, the title is more prominent than the sub title. This can be [confirmed visually in the screenshots in the API guide](https://toga.beeware.org/en/stable/reference/api/widgets/detailedlist). These screenshots should be updated as part of the PR addressing this issue. The "screenshots" example app can be used to generate the required screenshot images.

(Note: Edited by project maintainers to reflect consistent style between platforms)

Locate the DetailedList implementation and compare its Windows/Qt title and subtitle styling with the behavior on other platforms. Use the "screenshots" example app to generate updated images for the API guide. Done means the title uses the platform default font and size, the subtitle is 20% smaller, and the documented screenshots reflect the corrected appearance.

Written by the indexing model from the issue text.