Remove Iterative Lightening/Darkening

[lounsbrough]

Is your feature request related to a problem? Please describe.
There is a potential performance improvement.

Describe the solution you'd like
It would be great if we did not have to iteratively lighten/darken a color and keep checking if contrast has been satisfied, or that we can not lighten/darken any further.

Describe alternatives you've considered
I tried various formulas to try and compute the necessary lightness to apply to a color to achieve the target relative luminance. The various methods I tried got close, but were never quite right.

Additional context
The performance impact of the current solution seems to be minimal, but it would be cool to remove the lightening/darkening iteration at some point.