Constify ComputedNode (#16134)

# Objective

Make all the methods and associated functions belonging to
`ComputedNode` const.

## Solution

Constify (except for `inner_radius` which uses non-const `min` and
`max`).

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>

crates/bevy_ui/src/ui_node.rs

@@ -64,6 +64,7 @@ impl ComputedNode {
     /// The calculated node size as width and height in logical pixels.
     ///
     /// Automatically calculated by [`super::layout::ui_layout_system`].
+    #[inline]
     pub const fn size(&self) -> Vec2 {
         self.size
     }
@@ -71,8 +72,8 @@ impl ComputedNode {
     /// Check if the node is empty.
     /// A node is considered empty if it has a zero or negative extent along either of its axes.
     #[inline]
-    pub fn is_empty(&self) -> bool {
-        self.size().cmple(Vec2::ZERO).any()
+    pub const fn is_empty(&self) -> bool {
+        self.size.x <= 0. || self.size.y <= 0.
     }
 
     /// The order of the node in the UI layout.
@@ -86,6 +87,7 @@ impl ComputedNode {
     /// The calculated node size as width and height in logical pixels before rounding.
     ///
     /// Automatically calculated by [`super::layout::ui_layout_system`].
+    #[inline]
     pub const fn unrounded_size(&self) -> Vec2 {
         self.unrounded_size
     }
@@ -95,7 +97,7 @@ impl ComputedNode {
     ///
     /// Automatically calculated by [`super::layout::ui_layout_system`].
     #[inline]
-    pub fn outline_width(&self) -> f32 {
+    pub const fn outline_width(&self) -> f32 {
         self.outline_width
     }
 
@@ -103,7 +105,7 @@ impl ComputedNode {
     ///
     /// Automatically calculated by [`super::layout::ui_layout_system`].
     #[inline]
-    pub fn outline_offset(&self) -> f32 {
+    pub const fn outline_offset(&self) -> f32 {
         self.outline_offset
     }
 
@@ -111,8 +113,9 @@ impl ComputedNode {
     ///
     /// Automatically calculated by [`super::layout::ui_layout_system`].
     #[inline]
-    pub fn outlined_node_size(&self) -> Vec2 {
-        self.size() + 2. * (self.outline_offset + self.outline_width)
+    pub const fn outlined_node_size(&self) -> Vec2 {
+        let offset = 2. * (self.outline_offset + self.outline_width);
+        Vec2::new(self.size.x + offset, self.size.y + offset)
     }
 
     /// Returns the border radius for each corner of the outline
@@ -121,20 +124,20 @@ impl ComputedNode {
     ///
     /// Automatically calculated by [`super::layout::ui_layout_system`].
     #[inline]
-    pub fn outline_radius(&self) -> ResolvedBorderRadius {
+    pub const fn outline_radius(&self) -> ResolvedBorderRadius {
         let outer_distance = self.outline_width + self.outline_offset;
-        let compute_radius = |radius| {
+        const fn compute_radius(radius: f32, outer_distance: f32) -> f32 {
             if radius > 0. {
                 radius + outer_distance
             } else {
                 0.
             }
-        };
+        }
         ResolvedBorderRadius {
-            top_left: compute_radius(self.border_radius.top_left),
-            top_right: compute_radius(self.border_radius.top_right),
-            bottom_left: compute_radius(self.border_radius.bottom_left),
-            bottom_right: compute_radius(self.border_radius.bottom_right),
+            top_left: compute_radius(self.border_radius.top_left, outer_distance),
+            top_right: compute_radius(self.border_radius.top_right, outer_distance),
+            bottom_left: compute_radius(self.border_radius.bottom_left, outer_distance),
+            bottom_right: compute_radius(self.border_radius.bottom_right, outer_distance),
         }
     }
 
@@ -142,7 +145,7 @@ impl ComputedNode {
     ///
     /// Automatically calculated by [`super::layout::ui_layout_system`].
     #[inline]
-    pub fn border(&self) -> BorderRect {
+    pub const fn border(&self) -> BorderRect {
         self.border
     }
 
@@ -150,7 +153,7 @@ impl ComputedNode {
     ///
     /// Automatically calculated by [`super::layout::ui_layout_system`].
     #[inline]
-    pub fn border_radius(&self) -> ResolvedBorderRadius {
+    pub const fn border_radius(&self) -> ResolvedBorderRadius {
         self.border_radius
     }
 
@@ -180,13 +183,13 @@ impl ComputedNode {
     ///
     /// Automatically calculated by [`super::layout::ui_layout_system`].
     #[inline]
-    pub fn padding(&self) -> BorderRect {
+    pub const fn padding(&self) -> BorderRect {
         self.padding
     }
 
     /// Returns the combined inset on each edge including both padding and border thickness in logical pixels.
     #[inline]
-    pub fn content_inset(&self) -> BorderRect {
+    pub const fn content_inset(&self) -> BorderRect {
         BorderRect {
             left: self.border.left + self.padding.left,
             right: self.border.right + self.padding.right,