This patch beings the user interface of the applet and the KCM closer together. To
accomplish this, the following changes are made:
- Move the "Default Device" button onto the first row in the applet and make it a ToolButton to reduce its visual weight
- In both the applet and the KCM, show the port chooser UI in combobox form only when multiple ports are available; otherwise show only a text label. This is allowed by the HIG because it is a case of hardware availability (https://hig.kde.org/plattform/settings.html?highlight=inapplicable#behavior)
Depends on D24402