Solve some oklaba inconsistencies (#12526)

# Objective

- Even if we have `Laba` and `Oklcha` colorspaces using lightness as the
L field name, `Oklaba` doesn't do the same
- The shorthand function for creating a new color should be named
`Oklaba::lab`, but is named `lch`

## Solution

- Rename field l in `Oklaba` to lightness
- Rename `Oklaba::lch` to `Oklaba::lab`

---

## Changelog

### Changed
- Changed name in l field in `Oklaba` to lightness
- Changed method name `Oklaba::lch` to `Oklaba::lab`

## Migration Guide

If you were creating a Oklaba instance directly, instead of using L, you
should use lightness
```rust
// Before
let oklaba = Oklaba { l: 1., ..Default::default() };

// Now
let oklaba = Oklaba { lightness: 1., ..Default::default() };
``` 

if you were using the function `Oklaba::lch`, now the method is named
`Oklaba::lab`

crates/bevy_color/src/color.rs

@@ -266,14 +266,19 @@ impl Color {
     }
 
     /// Creates a new [`Color`] object storing a [`Oklaba`] color.
-    pub const fn oklaba(l: f32, a: f32, b: f32, alpha: f32) -> Self {
-        Self::Oklaba(Oklaba { l, a, b, alpha })
+    pub const fn oklaba(lightness: f32, a: f32, b: f32, alpha: f32) -> Self {
+        Self::Oklaba(Oklaba {
+            lightness,
+            a,
+            b,
+            alpha,
+        })
     }
 
     /// Creates a new [`Color`] object storing a [`Oklaba`] color with an alpha of 1.0.
-    pub const fn oklab(l: f32, a: f32, b: f32) -> Self {
+    pub const fn oklab(lightness: f32, a: f32, b: f32) -> Self {
         Self::Oklaba(Oklaba {
-            l,
+            lightness,
             a,
             b,
             alpha: 1.0,

crates/bevy_color/src/oklaba.rs

@@ -14,7 +14,7 @@ use serde::{Deserialize, Serialize};
 #[reflect(PartialEq, Serialize, Deserialize, Default)]
 pub struct Oklaba {
     /// The 'l' channel. [0.0, 1.0]
-    pub l: f32,
+    pub lightness: f32,
     /// The 'a' channel. [-1.0, 1.0]
     pub a: f32,
     /// The 'b' channel. [-1.0, 1.0]
@@ -30,33 +30,38 @@ impl Oklaba {
     ///
     /// # Arguments
     ///
-    /// * `l` - Lightness channel. [0.0, 1.0]
+    /// * `lightness` - Lightness channel. [0.0, 1.0]
     /// * `a` - Green-red channel. [-1.0, 1.0]
     /// * `b` - Blue-yellow channel. [-1.0, 1.0]
     /// * `alpha` - Alpha channel. [0.0, 1.0]
-    pub const fn new(l: f32, a: f32, b: f32, alpha: f32) -> Self {
-        Self { l, a, b, alpha }
+    pub const fn new(lightness: f32, a: f32, b: f32, alpha: f32) -> Self {
+        Self {
+            lightness,
+            a,
+            b,
+            alpha,
+        }
     }
 
     /// Construct a new [`Oklaba`] color from (l, a, b) components, with the default alpha (1.0).
     ///
     /// # Arguments
     ///
-    /// * `l` - Lightness channel. [0.0, 1.0]
+    /// * `lightness` - Lightness channel. [0.0, 1.0]
     /// * `a` - Green-red channel. [-1.0, 1.0]
     /// * `b` - Blue-yellow channel. [-1.0, 1.0]
-    pub const fn lch(l: f32, a: f32, b: f32) -> Self {
+    pub const fn lab(lightness: f32, a: f32, b: f32) -> Self {
         Self {
-            l,
+            lightness,
             a,
             b,
             alpha: 1.0,
         }
     }
 
     /// Return a copy of this color with the 'l' channel set to the given value.
-    pub const fn with_l(self, l: f32) -> Self {
-        Self { l, ..self }
+    pub const fn with_lightness(self, lightness: f32) -> Self {
+        Self { lightness, ..self }
     }
 
     /// Return a copy of this color with the 'a' channel set to the given value.
@@ -81,7 +86,7 @@ impl Mix for Oklaba {
     fn mix(&self, other: &Self, factor: f32) -> Self {
         let n_factor = 1.0 - factor;
         Self {
-            l: self.l * n_factor + other.l * factor,
+            lightness: self.lightness * n_factor + other.lightness * factor,
             a: self.a * n_factor + other.a * factor,
             b: self.b * n_factor + other.b * factor,
             alpha: self.alpha * n_factor + other.alpha * factor,
@@ -108,27 +113,39 @@ impl Alpha for Oklaba {
 
 impl Luminance for Oklaba {
     #[inline]
-    fn with_luminance(&self, l: f32) -> Self {
-        Self { l, ..*self }
+    fn with_luminance(&self, lightness: f32) -> Self {
+        Self { lightness, ..*self }
     }
 
     fn luminance(&self) -> f32 {
-        self.l
+        self.lightness
     }
 
     fn darker(&self, amount: f32) -> Self {
-        Self::new((self.l - amount).max(0.), self.a, self.b, self.alpha)
+        Self::new(
+            (self.lightness - amount).max(0.),
+            self.a,
+            self.b,
+            self.alpha,
+        )
     }
 
     fn lighter(&self, amount: f32) -> Self {
-        Self::new((self.l + amount).min(1.), self.a, self.b, self.alpha)
+        Self::new(
+            (self.lightness + amount).min(1.),
+            self.a,
+            self.b,
+            self.alpha,
+        )
     }
 }
 
 impl EuclideanDistance for Oklaba {
     #[inline]
     fn distance_squared(&self, other: &Self) -> f32 {
-        (self.l - other.l).powi(2) + (self.a - other.a).powi(2) + (self.b - other.b).powi(2)
+        (self.lightness - other.lightness).powi(2)
+            + (self.a - other.a).powi(2)
+            + (self.b - other.b).powi(2)
     }
 }
 
@@ -158,12 +175,17 @@ impl From<LinearRgba> for Oklaba {
 #[allow(clippy::excessive_precision)]
 impl From<Oklaba> for LinearRgba {
     fn from(value: Oklaba) -> Self {
-        let Oklaba { l, a, b, alpha } = value;
+        let Oklaba {
+            lightness,
+            a,
+            b,
+            alpha,
+        } = value;
 
         // From https://github.com/Ogeon/palette/blob/e75eab2fb21af579353f51f6229a510d0d50a311/palette/src/oklab.rs#L312-L332
-        let l_ = l + 0.3963377774 * a + 0.2158037573 * b;
-        let m_ = l - 0.1055613458 * a - 0.0638541728 * b;
-        let s_ = l - 0.0894841775 * a - 1.2914855480 * b;
+        let l_ = lightness + 0.3963377774 * a + 0.2158037573 * b;
+        let m_ = lightness - 0.1055613458 * a - 0.0638541728 * b;
+        let s_ = lightness - 0.0894841775 * a - 1.2914855480 * b;
 
         let l = l_ * l_ * l_;
         let m = m_ * m_ * m_;
@@ -266,7 +288,7 @@ mod tests {
         let oklaba = Oklaba::new(0.5, 0.5, 0.5, 1.0);
         let srgba: Srgba = oklaba.into();
         let oklaba2: Oklaba = srgba.into();
-        assert_approx_eq!(oklaba.l, oklaba2.l, 0.001);
+        assert_approx_eq!(oklaba.lightness, oklaba2.lightness, 0.001);
         assert_approx_eq!(oklaba.a, oklaba2.a, 0.001);
         assert_approx_eq!(oklaba.b, oklaba2.b, 0.001);
         assert_approx_eq!(oklaba.alpha, oklaba2.alpha, 0.001);
@@ -299,7 +321,7 @@ mod tests {
         let oklaba = Oklaba::new(0.5, 0.5, 0.5, 1.0);
         let linear: LinearRgba = oklaba.into();
         let oklaba2: Oklaba = linear.into();
-        assert_approx_eq!(oklaba.l, oklaba2.l, 0.001);
+        assert_approx_eq!(oklaba.lightness, oklaba2.lightness, 0.001);
         assert_approx_eq!(oklaba.a, oklaba2.a, 0.001);
         assert_approx_eq!(oklaba.b, oklaba2.b, 0.001);
         assert_approx_eq!(oklaba.alpha, oklaba2.alpha, 0.001);

crates/bevy_color/src/oklcha.rs

@@ -175,8 +175,14 @@ impl EuclideanDistance for Oklcha {
 }
 
 impl From<Oklaba> for Oklcha {
-    fn from(Oklaba { l, a, b, alpha }: Oklaba) -> Self {
-        let lightness = l;
+    fn from(
+        Oklaba {
+            lightness,
+            a,
+            b,
+            alpha,
+        }: Oklaba,
+    ) -> Self {
         let chroma = a.hypot(b);
         let hue = b.atan2(a).to_degrees();