Wire up per corner radii for quad

Still need to expose this in the styling layer and allow images
to have per corner radii.

crates/workspace/src/pane.rs

@@ -1397,7 +1397,7 @@ impl Pane {
                         bounds: square,
                         background: Some(color),
                         border: Default::default(),
-                        corner_radius: diameter / 2.,
+                        corner_radii: (diameter / 2.).into(),
                     });
                 }
             })

crates/workspace/src/pane/dragged_item_receiver.rs

@@ -61,7 +61,7 @@ where
                                 bounds: overlay_region,
                                 background: Some(overlay_color(cx)),
                                 border: Default::default(),
-                                corner_radius: 0.,
+                                corner_radii: Default::default(),
                             });
                         });
                     }

crates/workspace/src/workspace.rs

@@ -3614,7 +3614,7 @@ fn notify_of_new_dock(workspace: &WeakViewHandle<Workspace>, cx: &mut AsyncAppCo
                                 bounds,
                                 background: Some(code_span_background_color),
                                 border: Default::default(),
-                                corner_radius: 2.0,
+                                corner_radii: (2.0).into(),
                             })
                         })
                         .into_any()