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/tooltip.rs

@@ -1,12 +1,13 @@
 #![allow(missing_docs)]
 
-use gpui::{Action, AnyView, AppContext as _, FocusHandle, IntoElement, Render};
+use gpui::{Action, AnyElement, AnyView, AppContext as _, FocusHandle, IntoElement, Render};
 use settings::Settings;
 use theme::ThemeSettings;
 
 use crate::prelude::*;
 use crate::{h_flex, v_flex, Color, KeyBinding, Label, LabelSize, StyledExt};
 
+#[derive(IntoComponent)]
 pub struct Tooltip {
     title: SharedString,
     meta: Option<SharedString>,
@@ -204,3 +205,15 @@ impl Render for LinkPreview {
         })
     }
 }
+
+impl ComponentPreview for Tooltip {
+    fn preview(_window: &mut Window, _cx: &App) -> AnyElement {
+        example_group(vec![single_example(
+            "Text only",
+            Button::new("delete-example", "Delete")
+                .tooltip(Tooltip::text("This is a tooltip!"))
+                .into_any_element(),
+        )])
+        .into_any_element()
+    }
+}