Order of `<AsIs>` may disrupt scales.

[teunbrand]

If an <AsIs> aesthetic comes after a regular aesthetic, the <AsIs> vector is not scaled.
This is good, as this was a goal of #5477.

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

df <- data.frame(
  x = 1:4, y = 1:4,
  colour = c("red", "green", "blue", "yellow"),
  group  = LETTERS[1:4]
)

ggplot(df, aes(x, y)) +
  geom_text(aes(label = group, colour = group)) +
  geom_text(aes(x = 5 - x, label = colour, colour = I(colour)))

However, if the first layer has an <AsIs> aesthetic, the second layer with a regular aesthetic has problems.
This is because scale_{aes}_identity() is still being invoked in find_scale().
This is a problem because one of the goals of #5477 was to 'unclash' such scales.

ggplot(df, aes(x, y)) +
  geom_text(aes(x = 5 - x, label = colour, colour = I(colour))) +
  geom_text(aes(label = group, colour = group))
#> Error in `geom_text()`:
#> ! Problem while converting geom to grob.
#> ℹ Error occurred in the 2nd layer.
#> Caused by error:
#> ! Unknown colour name: A

^{Created on 2023-12-18 with reprex v2.0.2}

[teunbrand]

Considered fixed by #5597