keyboard: Set ornament on selected item in OSK languages popup menu

There is no hint about the currently selected language, but this exists in the mockups. Add a dot ornament on the language that is currently selected at the time of showing the OSK languages popup.

Since this popup is created from scratch every time it is shown, and the popup is tear down with the OSK during replacement. This also works for further times the languages popup is shown.

Closes: #5598 (closed)