[css-color-4] Use 0 chroma when hue is powerless during conversion #14133

https://drafts.csswg.org/css-color-4/#powerless-color-component

When performing color space conversion to a cylindrical polar color space, user agents shall treat a hue component as powerless if the chroma (or other measure of colorfulness, such as saturation in hsl) is less than the epsilon (ε) specified for that color space. For example, a gray color converted into oklch() may, due to numerical errors, have an extremely small chroma rather than precisely 0%; as a result, the hue component is powerless.

https://drafts.csswg.org/css-color-4/#specifying-oklab-oklch

Powerless hue ε C <= 0.000004

So hue is powerless when chroma is smaller than 0.000004 but chroma itself is not set to 0.
And any missing component is treated as 0 for the actual conversion math.

So color(from oklch(0.5 0.000004 180) display-p3 r g b) which should have a powerless hue still ends up as: color(display-p3 0.38857936 0.38856994 0.38857244)

Converting that to hsl for example results in color(srgb 0.38858148 0.38856954 0.3885725).

Shouldn't chroma/saturation also be set to 0 when it matches the powerless hue condition? Otherwise the outcome is a color with whatever hue 0deg is for a given color space. This hue might itself be powerless, but when converting to polar spaces it will still surface.

@svgeesus