⚠️ Rename Rounding to CornerRadius (#5673)

Breaking change!

* `Rounding` -> `CornerRadius`
* `rounding` -> `corner_radius`

This is to:
* Clarify
* Conform to other systems (e.g. Figma)
* Avoid confusion with `GuiRounding`

crates/epaint/src/shapes/rect_shape.rs

@@ -10,7 +10,7 @@ pub struct RectShape {
 
     /// How rounded the corners of the rectangle are.
     ///
-    /// Use `Rounding::ZERO` for for sharp corners.
+    /// Use [`CornerRadius::ZERO`] for for sharp corners.
     ///
     /// This is the corner radii of the rectangle.
     /// If there is a stroke, then the stroke will have an inner and outer corner radius,
@@ -18,7 +18,7 @@ pub struct RectShape {
     ///
     /// For [`StrokeKind::Inside`], the outside of the stroke coincides with the rectangle,
     /// so the rounding will in this case specify the outer corner radius.
-    pub rounding: Rounding,
+    pub corner_radius: CornerRadius,
 
     /// How to fill the rectangle.
     pub fill: Color32,
@@ -73,14 +73,14 @@ impl RectShape {
     #[inline]
     pub fn new(
         rect: Rect,
-        rounding: impl Into<Rounding>,
+        corner_radius: impl Into<CornerRadius>,
         fill_color: impl Into<Color32>,
         stroke: impl Into<Stroke>,
         stroke_kind: StrokeKind,
     ) -> Self {
         Self {
             rect,
-            rounding: rounding.into(),
+            corner_radius: corner_radius.into(),
             fill: fill_color.into(),
             stroke: stroke.into(),
             stroke_kind,
@@ -93,12 +93,12 @@ impl RectShape {
     #[inline]
     pub fn filled(
         rect: Rect,
-        rounding: impl Into<Rounding>,
+        corner_radius: impl Into<CornerRadius>,
         fill_color: impl Into<Color32>,
     ) -> Self {
         Self::new(
             rect,
-            rounding,
+            corner_radius,
             fill_color,
             Stroke::NONE,
             StrokeKind::Outside, // doesn't matter
@@ -108,12 +108,12 @@ impl RectShape {
     #[inline]
     pub fn stroke(
         rect: Rect,
-        rounding: impl Into<Rounding>,
+        corner_radius: impl Into<CornerRadius>,
         stroke: impl Into<Stroke>,
         stroke_kind: StrokeKind,
     ) -> Self {
         let fill = Color32::TRANSPARENT;
-        Self::new(rect, rounding, fill, stroke, stroke_kind)
+        Self::new(rect, corner_radius, fill, stroke, stroke_kind)
     }
 
     /// Set if the stroke is on the inside, outside, or centered on the rectangle.