Feature request: method for position guides to request additional space

[teunbrand]

This is a bit of a selfish request, but I think it might be nice if axis guides can request additional space in the orthogonal direction.
Currently, an x-axis can determine its height and a y-axis its width, but there might be reasons for guides to extend beyond the panel borders in the opposite direction.

The main use case I have in mind for this feature is to ensure that there is ample space to display side-titles (displ, cty, hwy, class) in plots like these:

[teunbrand]

I don't really see a clean way to do this, so I'm going to go ahead and close this.