Implement Container widget

Remove `align_self` and `justify_content` methods

native/src/widget/container.rs

@@ -0,0 +1,93 @@
+use std::hash::Hash;
+
+use crate::{
+    layout, Element, Event, Hasher, Layout, Length, Point, Size, Widget,
+};
+
+/// A container that distributes its contents vertically.
+pub type Container<'a, Message, Renderer> =
+    iced_core::Container<Element<'a, Message, Renderer>>;
+
+impl<'a, Message, Renderer> Widget<Message, Renderer>
+    for Container<'a, Message, Renderer>
+where
+    Renderer: crate::Renderer,
+{
+    fn width(&self) -> Length {
+        self.width
+    }
+
+    fn layout(
+        &self,
+        renderer: &Renderer,
+        limits: &layout::Limits,
+    ) -> layout::Node {
+        let limits = limits
+            .loose()
+            .max_width(self.max_width)
+            .max_height(self.max_height)
+            .width(self.width)
+            .height(self.height);
+
+        let mut content = self.content.layout(renderer, &limits);
+        let size = limits.resolve(content.size());
+
+        content.align(self.horizontal_alignment, self.vertical_alignment, size);
+
+        layout::Node::with_children(size, vec![content])
+    }
+
+    fn on_event(
+        &mut self,
+        event: Event,
+        layout: Layout<'_>,
+        cursor_position: Point,
+        messages: &mut Vec<Message>,
+        renderer: &Renderer,
+    ) {
+        self.content.widget.on_event(
+            event,
+            layout.children().next().unwrap(),
+            cursor_position,
+            messages,
+            renderer,
+        )
+    }
+
+    fn draw(
+        &self,
+        renderer: &mut Renderer,
+        layout: Layout<'_>,
+        cursor_position: Point,
+    ) -> Renderer::Output {
+        self.content.draw(
+            renderer,
+            layout.children().next().unwrap(),
+            cursor_position,
+        )
+    }
+
+    fn hash_layout(&self, state: &mut Hasher) {
+        0.hash(state);
+        self.width.hash(state);
+        self.height.hash(state);
+        self.max_width.hash(state);
+        self.max_height.hash(state);
+        self.padding.hash(state);
+
+        self.content.hash_layout(state);
+    }
+}
+
+impl<'a, Message, Renderer> From<Container<'a, Message, Renderer>>
+    for Element<'a, Message, Renderer>
+where
+    Renderer: 'a + crate::Renderer,
+    Message: 'static,
+{
+    fn from(
+        column: Container<'a, Message, Renderer>,
+    ) -> Element<'a, Message, Renderer> {
+        Element::new(column)
+    }
+}