component: Add component and component_preview crates to power UI components (#24456)

This PR formalizes design components with the Component and
ComponentPreview traits.

You can open the preview UI with `workspace: open component preview`.

Component previews no longer need to return `Self` allowing for more
complex previews, and previews of components like `ui::Tooltip` that
supplement other components rather than are rendered by default.

`cargo-machete` incorrectly identifies `linkme` as an unused dep on
crates that have components deriving `IntoComponent`, so you may need to
add this to that crate's `Cargo.toml`:

```toml
# cargo-machete doesn't understand that linkme is used in the component macro
[package.metadata.cargo-machete]
ignored = ["linkme"]
```

Release Notes:

- N/A

---------

Co-authored-by: Marshall Bowers <git@maxdeviant.com>

crates/ui/src/components/tab.rs

@@ -27,7 +27,7 @@ pub enum TabCloseSide {
     End,
 }
 
-#[derive(IntoElement)]
+#[derive(IntoElement, IntoComponent)]
 pub struct Tab {
     div: Stateful<Div>,
     selected: bool,
@@ -171,3 +171,48 @@ impl RenderOnce for Tab {
             )
     }
 }
+
+impl ComponentPreview for Tab {
+    fn preview(_window: &mut Window, _cx: &App) -> AnyElement {
+        v_flex()
+            .gap_6()
+            .children(vec![example_group_with_title(
+                "Variations",
+                vec![
+                    single_example(
+                        "Default",
+                        Tab::new("default").child("Default Tab").into_any_element(),
+                    ),
+                    single_example(
+                        "Selected",
+                        Tab::new("selected")
+                            .toggle_state(true)
+                            .child("Selected Tab")
+                            .into_any_element(),
+                    ),
+                    single_example(
+                        "First",
+                        Tab::new("first")
+                            .position(TabPosition::First)
+                            .child("First Tab")
+                            .into_any_element(),
+                    ),
+                    single_example(
+                        "Middle",
+                        Tab::new("middle")
+                            .position(TabPosition::Middle(Ordering::Equal))
+                            .child("Middle Tab")
+                            .into_any_element(),
+                    ),
+                    single_example(
+                        "Last",
+                        Tab::new("last")
+                            .position(TabPosition::Last)
+                            .child("Last Tab")
+                            .into_any_element(),
+                    ),
+                ],
+            )])
+            .into_any_element()
+    }
+}