GtkTooltip: Scale the cursor size on X11
GtkSettings/X11 takes the values as directly provided by XSettings, which reports physical sizes. Other backends instead report logical sizes (logical values are needed in order to support mixed-DPI setups, but X11 doesn't support mixed DPI setups anyway).
Take that in account when retrieving the cursor size in gtk_tooltip_position ().
Note that this discrepancy between the X11 and other backends has been fixed in GTK4.
Fixes #5223
Edited by Luca Bacci