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}

[thomasp85]

I might misremember but wasn't scale reversing by supplying a reversed limit a thing/feature? If so, this would break it, right?

[teunbrand]

This was discussed a little bit in the linked issue (TL;DR: it isn't properly documented in ggplot2), but yes this would definitly break such thing if it were a feature.

[thomasp85]

okay - I'm a bit uneasy about this, just because I anticipate it will break many peoples code (many is maybe a bit too strong, but a non-negligible number)

[teunbrand]

Yeah that's fair, but if we decide that is a proper feature, then it should be documented somewhere and implemented consistently.

[thomasp85]

Yeah, I agree. We can discuss at a meeting where to go with this

[teunbrand]

Closing this in favour of #6070