Scales with no matching data throw warnings

[teunbrand]

This PR aims to fix #3743.

Briefly, a warning is thrown when a scale was declared, but none of the data has the relevant aesthetic.

I had to touch the build method to coordinate this warning, but if extensions don't update they should skip the warning, so it should be safe.

Reprex from issue:

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

ggplot(iris, aes(x = Species, y = Sepal.Length, fill = Species)) +
  geom_boxplot() +
  scale_colour_brewer(
    name = 'Dude which plant',
    palette = 'Set2'
  )
#> Warning in scale_colour_brewer(name = "Dude which plant", palette = "Set2"):
#> Scale for colour aesthetic was provided but has no matching data to map.

^{Created on 2024-05-27 with reprex v2.1.0}

[teunbrand]

I'm closing this, there are too many spurious cases where this warning is thrown