Binned limits and reverse transform

[teunbrand]

This PR aims to fix #5355.

Briefly, it now accepts NA in the limits to fill in the 'natural' limits, by using the continuous scale's get_limits(). Also, it tracks if limits have been supplied in reverse order and handles breaks correspondingly.

Small demo:

devtools::load_all("~/packages/ggplot2")
#> ℹ Loading ggplot2
library(patchwork)

p <- ggplot(mtcars) + geom_bar(aes(mpg))

p1 <- p + scale_x_binned()
p2 <- p + scale_x_binned(
  trans = "reverse", 
  right = FALSE # Just to be symmetrical with p1
) 

p1 | p2

^{Created on 2023-07-19 with reprex v2.0.2}

[thomasp85]

LGTM

[teunbrand]

Thanks for the review!