This PR improves colors with alpha values where the alpha value results
in 100%.
Before this change, a class like `bg-red-500/100` would be generated as:
```css
.bg-red-500\/100 {
background-color: #ef4444;
}
@supports (color: color-mix(in lab, red, red)) {
.bg-red-500\/100 {
background-color: color-mix(in oklab, var(--color-red-500) 100%, transparent);
}
}
```
But we don't need the `color-mix`, or the fallback styles at all in case
the alpha value is 100%.
After this change the `bg-red-500/100` class will generate as:
```css
.bg-red-500\/100 {
background-color: var(--color-red-500);
}
```
Which is essentially the same as `bg-red-500`, but we can migrate that
away in the future. At least the generated CSS is smaller.
## Test plan
1. Added a test to ensure the generated value doesn't include color-mix
at all.
d2daf59524