Fix inconsistent naming of tree parameter in Widget trait (#2950)

* fix inconsistent naming of tree parameter in widget trait

* rename `Tree` parameter in various usages across iced

core/src/element.rs

@@ -435,19 +435,19 @@ where
 
     fn operate(
         &mut self,
-        state: &mut Tree,
+        tree: &mut Tree,
         layout: Layout<'_>,
         renderer: &Renderer,
         operation: &mut dyn widget::Operation,
     ) {
         self.element
             .widget
-            .operate(state, layout, renderer, operation);
+            .operate(tree, layout, renderer, operation);
     }
 
     fn update(
         &mut self,
-        state: &mut Tree,
+        tree: &mut Tree,
         event: &Event,
         layout: Layout<'_>,
         cursor: mouse::Cursor,
@@ -457,13 +457,13 @@ where
         viewport: &Rectangle,
     ) {
         self.element.widget.update(
-            state, event, layout, cursor, renderer, clipboard, shell, viewport,
+            tree, event, layout, cursor, renderer, clipboard, shell, viewport,
         );
     }
 
     fn draw(
         &self,
-        state: &Tree,
+        tree: &Tree,
         renderer: &mut Renderer,
         theme: &Theme,
         style: &renderer::Style,
@@ -496,7 +496,7 @@ where
 
         self.element
             .widget
-            .draw(state, renderer, theme, style, layout, cursor, viewport);
+            .draw(tree, renderer, theme, style, layout, cursor, viewport);
 
         renderer.with_layer(Rectangle::INFINITE, |renderer| {
             explain_layout(renderer, self.color, layout);
@@ -505,7 +505,7 @@ where
 
     fn mouse_interaction(
         &self,
-        state: &Tree,
+        tree: &Tree,
         layout: Layout<'_>,
         cursor: mouse::Cursor,
         viewport: &Rectangle,
@@ -513,19 +513,19 @@ where
     ) -> mouse::Interaction {
         self.element
             .widget
-            .mouse_interaction(state, layout, cursor, viewport, renderer)
+            .mouse_interaction(tree, layout, cursor, viewport, renderer)
     }
 
     fn overlay<'b>(
         &'b mut self,
-        state: &'b mut Tree,
+        tree: &'b mut Tree,
         layout: Layout<'b>,
         renderer: &Renderer,
         viewport: &Rectangle,
         translation: Vector,
     ) -> Option<overlay::Element<'b, Message, Theme, Renderer>> {
         self.element.widget.overlay(
-            state,
+            tree,
             layout,
             renderer,
             viewport,

core/src/widget.rs

@@ -99,7 +99,7 @@ where
     /// Applies an [`Operation`] to the [`Widget`].
     fn operate(
         &mut self,
-        _state: &mut Tree,
+        _tree: &mut Tree,
         _layout: Layout<'_>,
         _renderer: &Renderer,
         _operation: &mut dyn Operation,
@@ -111,7 +111,7 @@ where
     /// By default, it does nothing.
     fn update(
         &mut self,
-        _state: &mut Tree,
+        _tree: &mut Tree,
         _event: &Event,
         _layout: Layout<'_>,
         _cursor: mouse::Cursor,
@@ -127,7 +127,7 @@ where
     /// By default, it returns [`mouse::Interaction::None`].
     fn mouse_interaction(
         &self,
-        _state: &Tree,
+        _tree: &Tree,
         _layout: Layout<'_>,
         _cursor: mouse::Cursor,
         _viewport: &Rectangle,
@@ -139,7 +139,7 @@ where
     /// Returns the overlay of the [`Widget`], if there is any.
     fn overlay<'a>(
         &'a mut self,
-        _state: &'a mut Tree,
+        _tree: &'a mut Tree,
         _layout: Layout<'a>,
         _renderer: &Renderer,
         _viewport: &Rectangle,

core/src/widget/text.rs

@@ -245,7 +245,7 @@ where
 
     fn operate(
         &mut self,
-        _state: &mut Tree,
+        _tree: &mut Tree,
         layout: Layout<'_>,
         _renderer: &Renderer,
         operation: &mut dyn super::Operation,