style: Add lab(), lch(), oklab(), oklch() to specified colors

Use new changes from cssparser and use the new lab/lch/oklab/oklch color
formats.

Introduced a new color type AbsoluteColor.  It represents any kind of
color that has absolute numerical values.  It is also tied to a color
space and therefore can be trivially converted to another color space.

Differential Revision: https://phabricator.services.mozilla.com/D163579

components/style/gecko/values.rs

@@ -18,20 +18,18 @@ use std::cmp::max;
 
 /// Convert a given RGBA value to `nscolor`.
 pub fn convert_rgba_to_nscolor(rgba: &RGBA) -> u32 {
-    ((rgba.alpha as u32) << 24) |
-        ((rgba.blue as u32) << 16) |
-        ((rgba.green as u32) << 8) |
-        (rgba.red as u32)
+    u32::from_le_bytes([
+        rgba.red,
+        rgba.green,
+        rgba.blue,
+        (rgba.alpha * 255.0).round() as u8,
+    ])
 }
 
 /// Convert a given `nscolor` to a Servo RGBA value.
 pub fn convert_nscolor_to_rgba(color: u32) -> RGBA {
-    RGBA::new(
-        (color & 0xff) as u8,
-        (color >> 8 & 0xff) as u8,
-        (color >> 16 & 0xff) as u8,
-        (color >> 24 & 0xff) as u8,
-    )
+    let [r, g, b, a] = color.to_le_bytes();
+    RGBA::new(r, g, b, a as f32 / 255.0)
 }
 
 /// Round `width` down to the nearest device pixel, but any non-zero value that