Replace sf_rescale01_x() with scales::rescale()

[teunbrand]

This PR fixes a personal pet peeve of mine.

First, let me start by apologising for the tone of this PR.
The two functions in the title are in principle doing the same operation, but scales::rescale() supports more data types than just numeric.
Every time I look at coord_sf()'s code, I have to remind myself that they're really doing the same thing despite being named differently. If this PR gets merged, this saves me 5 seconds of my life every time I'm dealing with coord_sf().

Ulterior motive is also that I might want to feed not-bare-numeric data to coord_sf() at some point with a custom rescale method.

Typical coords use the Scale$rescaler() method. However, as the geometry column cannot be transformed by rescale(), we should not use the Scale$rescaler() method. If we did, annotations such as graticules and axis positions can become out of sync when a user has somehow engineered a non-standard rescaler in a position scale.

[thomasp85]

Can you see any indication of the need for the old function?

[teunbrand]

I don't think sf_rescale01_x() is needed. It was introduced in 379df62, I think as a pointwise equivalent to sf_rescale01(), which in turn is just scales::rescale().

[thomasp85]

LGTM