Sort scale and viewscale limits

[teunbrand]

This PR aims to fix #5918.

Briefly, continuous_scale() now sorts the limits and position guides get passed sorted ranges.

The order of the limits should now only matter when choosing e.g. limits = c(NA, 10) to substitute the NA for the data limits. Examples below are from the issue.

Regular scale, flipped limits:

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

ggplot() + scale_x_continuous(limits = c(10, 0))

Reverse scale, sorted limits:

ggplot() + scale_x_reverse(limits = c(0, 10))

^{Created on 2024-05-31 with reprex v2.1.0}