Fix broken Oklab color space matrices and conversions.

[patternspandemic]

Hello.

This PR resolves what seems to be a big of mix up with the Oklab color space functions, naming, and its use of the srgb <--> (linear)rgb conversion functions.

I think transformation functionality was misnamed and/or put into the wrong files in the two different conversion scenarios: oklab2(s)rgb and (s)rgb2oklab. This problem was then exacerbated by using the wrong order of linear (rgb) and non-linear (srgb) transformations, probably due to the naming and placement of functionality.
For example,

• the current oklab2srgb file actually converts oklab to (linear)rgb, but is named as converting to sRGB.
• the current oklab2rgb file uses the incorrectly named oklab2srgb to perform a correct transform of oklab->linear, but then incorrectly uses srgb2rgb (a double transform to linear).
• the current rgb2oklab converts (linear)rgb to sRGB (even though its already linear) probably because the actual transform functionality was put into srgb2okab.
• the current srgb2oklab actually converts (linear)rgb to oklab, but is named as converting from sRGB.

For testing, I used this pinkish color and the srgb and oklab derived values provided by the color picker functionality. I could not achieve results that were expected with any combination of current functions. These incorrect results can be seen by using this Oklab tester shader which I creatred to confirm this fix. With existing code, the color turned out on the lime green side of things rather than pinkish. With this fix, the expected results are a 2x2 grid of the same pinkish color.

I think there may have been one or two errors in the transform matrices involved. I have replaced them with the current ones found at the resource here, which I utilized to perform this fix:
Converting from linear sRGB to Oklab
Use a linear version of sRGB

I can only confirm the glsl functionality works as I expect, and was unable to test the updated hlsh/wgsl code.

Cheers, Brad

[patriciogonzalezvivo]

Thank you so much!