Rename corner_radius to rounding

Also update changelogs and clean up other aspects of
https://github.com/emilk/egui/pull/1206

egui_demo_lib/src/apps/demo/drag_and_drop.rs

@@ -66,7 +66,7 @@ pub fn drop_target<R>(
     ui.painter().set(
         where_to_put_background,
         epaint::RectShape {
-            corner_radius: style.corner_radius,
+            rounding: style.rounding,
             fill,
             stroke,
             rect,

egui_demo_lib/src/apps/demo/misc_demo_window.rs

@@ -269,7 +269,7 @@ impl ColorWidgets {
 #[cfg_attr(feature = "serde", serde(default))]
 struct BoxPainting {
     size: Vec2,
-    corner_radius: f32,
+    rounding: f32,
     stroke_width: f32,
     num_boxes: usize,
 }
@@ -278,7 +278,7 @@ impl Default for BoxPainting {
     fn default() -> Self {
         Self {
             size: vec2(64.0, 32.0),
-            corner_radius: 5.0,
+            rounding: 5.0,
             stroke_width: 2.0,
             num_boxes: 1,
         }
@@ -289,7 +289,7 @@ impl BoxPainting {
     pub fn ui(&mut self, ui: &mut Ui) {
         ui.add(Slider::new(&mut self.size.x, 0.0..=500.0).text("width"));
         ui.add(Slider::new(&mut self.size.y, 0.0..=500.0).text("height"));
-        ui.add(Slider::new(&mut self.corner_radius, 0.0..=50.0).text("corner_radius"));
+        ui.add(Slider::new(&mut self.rounding, 0.0..=50.0).text("rounding"));
         ui.add(Slider::new(&mut self.stroke_width, 0.0..=10.0).text("stroke_width"));
         ui.add(Slider::new(&mut self.num_boxes, 0..=8).text("num_boxes"));
 
@@ -298,7 +298,7 @@ impl BoxPainting {
                 let (rect, _response) = ui.allocate_at_least(self.size, Sense::hover());
                 ui.painter().rect(
                     rect,
-                    self.corner_radius,
+                    self.rounding,
                     Color32::from_gray(64),
                     Stroke::new(self.stroke_width, Color32::WHITE),
                 );

egui_demo_lib/src/frame_history.rs

@@ -76,7 +76,7 @@ impl FrameHistory {
         let mut shapes = Vec::with_capacity(3 + 2 * history.len());
         shapes.push(Shape::Rect(epaint::RectShape {
             rect,
-            corner_radius: style.corner_radius,
+            rounding: style.rounding,
             fill: ui.visuals().extreme_bg_color,
             stroke: ui.style().noninteractive().bg_stroke,
         }));