For the user anyway, all different mappings will look the same. It makes
no sense to make this more complicated for them by separating them into
different concepts.
ratbag's key mapping signature is forcing us to treat modifiers
different from regular keys. To detect them, we need several workarounds
over Gdk.EventKey which makes the code uglier than it could be. Perhaps
we should just skip this altogether and implement macros only; since
they don't differentiate between modifiers and regular keys all these
workaround can then be removed while providing the same functionality.
