Always save the window state and geometry

This includes the toolbar/menubar/dockwidget states (i.e. the State= config
key), and the window geometry. I was wrong to think the State= key included
the window geometry.

Depending on the "remeber window size" setting, we can apply the size saved
in the config file or the size from the profile settings (lines x columns),
which is included in MainWindow::sizeHint().

BUG: 442252
FIXED-IN: 21.12