Create iced_widget subcrate and re-organize the whole codebase

native/src/widget/pane_grid/draggable.rs

@@ -1,12 +0,0 @@
-use crate::{Layout, Point};
-
-/// A pane that can be dragged.
-pub trait Draggable {
-    /// Returns whether the [`Draggable`] with the given [`Layout`] can be picked
-    /// at the provided cursor position.
-    fn can_be_dragged_at(
-        &self,
-        layout: Layout<'_>,
-        cursor_position: Point,
-    ) -> bool;
-}