ui2: Reorganize components (#3228)

This PR reorganizes the components in the `ui2` crate.

The distinction between "elements" and "components" is now gone, with
all of the reusable components living under `components/`.

The components that we built while prototyping but will eventually live
in other crates currently reside in the `to_extract/` module.

Release Notes:

- N/A

crates/ui2/src/to_extract/copilot.rs

@@ -0,0 +1,46 @@
+use crate::{prelude::*, Button, Label, LabelColor, Modal};
+
+#[derive(Component)]
+pub struct CopilotModal {
+    id: ElementId,
+}
+
+impl CopilotModal {
+    pub fn new(id: impl Into<ElementId>) -> Self {
+        Self { id: id.into() }
+    }
+
+    fn render<V: 'static>(self, _view: &mut V, cx: &mut ViewContext<V>) -> impl Component<V> {
+        div().id(self.id.clone()).child(
+            Modal::new("some-id")
+                .title("Connect Copilot to Zed")
+                .child(Label::new("You can update your settings or sign out from the Copilot menu in the status bar.").color(LabelColor::Muted))
+                .primary_action(Button::new("Connect to Github").variant(ButtonVariant::Filled)),
+        )
+    }
+}
+
+#[cfg(feature = "stories")]
+pub use stories::*;
+
+#[cfg(feature = "stories")]
+mod stories {
+    use gpui2::{Div, Render};
+
+    use crate::Story;
+
+    use super::*;
+
+    pub struct CopilotModalStory;
+
+    impl Render for CopilotModalStory {
+        type Element = Div<Self>;
+
+        fn render(&mut self, cx: &mut ViewContext<Self>) -> Self::Element {
+            Story::container(cx)
+                .child(Story::title_for::<_, CopilotModal>(cx))
+                .child(Story::label(cx, "Default"))
+                .child(CopilotModal::new("copilot-modal"))
+        }
+    }
+}