Deprecate appropriately

[mdsumner]

tidyverse/ggplot2#3128

Update the hole story too, will be a nice link to mesh_plot speed

[mdsumner]

Here's how it works in R3.6.0, you can't use MULTIPOLYGON

 iw <- sf::read_sf(system.file("extdata", "inlandwaters.gpkg", package = "polyggon"))
 ggplot(spbabel::sptable(sf::st_cast(iw, "POLYGON")) %>% 
    dplyr::mutate(sg = paste(object_, branch_, sep = "_")), 
   aes(x_, y_, fill = object_, group = object_, subgroup = sg)) + 
  geom_polygon()