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/components/details.rs

@@ -0,0 +1,78 @@
+use crate::prelude::*;
+use crate::{v_stack, ButtonGroup};
+
+#[derive(Component)]
+pub struct Details<V: 'static> {
+    text: &'static str,
+    meta: Option<&'static str>,
+    actions: Option<ButtonGroup<V>>,
+}
+
+impl<V: 'static> Details<V> {
+    pub fn new(text: &'static str) -> Self {
+        Self {
+            text,
+            meta: None,
+            actions: None,
+        }
+    }
+
+    pub fn meta_text(mut self, meta: &'static str) -> Self {
+        self.meta = Some(meta);
+        self
+    }
+
+    pub fn actions(mut self, actions: ButtonGroup<V>) -> Self {
+        self.actions = Some(actions);
+        self
+    }
+
+    fn render(self, _view: &mut V, cx: &mut ViewContext<V>) -> impl Component<V> {
+        v_stack()
+            .p_1()
+            .gap_0p5()
+            .text_xs()
+            .text_color(cx.theme().colors().text)
+            .size_full()
+            .child(self.text)
+            .children(self.meta.map(|m| m))
+            .children(self.actions.map(|a| a))
+    }
+}
+
+#[cfg(feature = "stories")]
+pub use stories::*;
+
+#[cfg(feature = "stories")]
+mod stories {
+    use super::*;
+    use crate::{Button, Story};
+    use gpui2::{Div, Render};
+
+    pub struct DetailsStory;
+
+    impl Render for DetailsStory {
+        type Element = Div<Self>;
+
+        fn render(&mut self, cx: &mut ViewContext<Self>) -> Self::Element {
+            Story::container(cx)
+                .child(Story::title_for::<_, Details<Self>>(cx))
+                .child(Story::label(cx, "Default"))
+                .child(Details::new("The quick brown fox jumps over the lazy dog"))
+                .child(Story::label(cx, "With meta"))
+                .child(
+                    Details::new("The quick brown fox jumps over the lazy dog")
+                        .meta_text("Sphinx of black quartz, judge my vow."),
+                )
+                .child(Story::label(cx, "With meta and actions"))
+                .child(
+                    Details::new("The quick brown fox jumps over the lazy dog")
+                        .meta_text("Sphinx of black quartz, judge my vow.")
+                        .actions(ButtonGroup::new(vec![
+                            Button::new("Decline"),
+                            Button::new("Accept").variant(crate::ButtonVariant::Filled),
+                        ])),
+                )
+        }
+    }
+}