Can we deprecate fatten arg of geom_pointrange()?

[yutannihilation]

A follow up of #3672. Related to #4872, #2798

In my understanding, fatten was a workaround for the inability of controlling the point size and the line width differently. So, now that https://github.com/tidyverse/ggplot2/pull/3672 gets merged, I think geom_pointrange() no longer needs this parameter.

[yutannihilation]

Thinking this again, geom_crossbar() still needs fatten on the other hand because the middle bar is also line, not point. So, this seems a bit complicated than I thought. Anyway I think we need to clarify the relationship between size, linewidth, and fatten.

[thomasp85]

yeah, I think we may push this to the release after this in order to make the transition a bit smoother?

[yutannihilation]

If there's no downside, I think it's nice if we can include this in v3.4.0. It might be another good example to show why separating linewidth from size is useful.