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_macros/src/ui_macros.rs

@@ -1,3 +1,4 @@
+mod derive_component;
 mod derive_path_str;
 mod dynamic_spacing;
 
@@ -58,3 +59,27 @@ pub fn path_str(_args: TokenStream, input: TokenStream) -> TokenStream {
 pub fn derive_dynamic_spacing(input: TokenStream) -> TokenStream {
     dynamic_spacing::derive_spacing(input)
 }
+
+/// Derives the `Component` trait for a struct.
+///
+/// This macro generates implementations for the `Component` trait and associated
+/// registration functions for the component system.
+///
+/// # Attributes
+///
+/// - `#[component(scope = "...")]`: Required. Specifies the scope of the component.
+/// - `#[component(description = "...")]`: Optional. Provides a description for the component.
+///
+/// # Example
+///
+/// ```
+/// use ui_macros::Component;
+///
+/// #[derive(Component)]
+/// #[component(scope = "toggle", description = "A element that can be toggled on and off")]
+/// struct Checkbox;
+/// ```
+#[proc_macro_derive(IntoComponent, attributes(component))]
+pub fn derive_component(input: TokenStream) -> TokenStream {
+    derive_component::derive_into_component(input)
+}