Fix NaN okhsl/okhsv values when lightness approximates 0 or 1

[beicause]

Objective

Fixes the issues found in #24678 (comment) because LinearRgba::new(1.0, 1.0, 0.9999996, 1.0) converted to Okhsla { hue: 104.03624, saturation: NaN, lightness: 1.0, alpha: 1.0 } which contains NaN.

This happens when oklab_l == 0 or 1 while C != 0, e.g. white minus epsilon

Solution

Early return okhsl/okhsv when oklab lightness approximates 0 or 1.

Testing

Added more color tests.

With this fix the okhsl lightness slider looks correct:

[kfc35]

This happens when oklab_l == 0 or 1 while C != 0,

May be a stupid question, but I noticed you also changed the if to check whether C == 0. Would that suffice instead, meaning that you won’t have to early out for oklab_l == 0 or 1? Or is it that just an unrelated clarification

[beicause]

This happens when oklab_l == 0 or 1 while C != 0,

May be a stupid question, but I noticed you also changed the if to check whether C == 0. Would that suffice instead, meaning that you won’t have to early out for oklab_l == 0 or 1? Or is it that just an unrelated clarification

Both are needed.

We already checked C isn't 0. I just removed f32::EPSILON as it's arbitrary and doesn't have a good reason.