Coord flip grid

[teunbrand]

This PR aims to fix #6293.

Briefly, the flip coord transform swaps the 'x' and 'y' names which makes sense for layers, but not so much the panel grid as it already recieves the variables in flipped form. The solution is to flip again before going into coord transform.

The reprex from the issue, notice the ticks and grid lining up again:

devtools::load_all("~/packages/ggplot2/")
#> ℹ Loading ggplot2
x <- -1:10
y <- -1:10
dati <- as.data.frame(x,y)

ggplot(dati, aes(x = x, y = y)) +
  geom_point() +
  scale_x_continuous(breaks = seq(-15, 15, by = 3), 
                     limits = c(-15,15)) +
  coord_flip()+
  theme(panel.grid.major = element_line(color = "blue"),
        panel.grid.minor = element_line(color = "red"))

^{Created on 2025-02-05 with reprex v2.1.1}