Review supersession

[teunbrand]

It'd be helpful to review which functions have preferred alternatives and mark them as superseded.
As an example, coord_polar() can be replaced with coord_radial(), but isn't documented like that.
I'd expect some helper functions to be functionally superseded as well.

[teunbrand]

Let's create a list. It's open for additional suggestions.

Already superseded:

• coord_flip() by inverting x/y aesthetics.
• annotation_logticks() by guide_axis_logticks().
• coord_map() and coord_quickmap() by coord_sf()

Considered for supersession:

• coord_polar() to be superseded by coord_radial()
• coord_equal() to be superseded by coord_fixed()
  • Perhaps these could even be incorporated in coord_cartesian(), they are easy to implement.
• expand_limits() should just be function to be passed to scale limits, e.g. limits = ~ range(.x, value).