Toggle & Switch (#21979)

![CleanShot 2024-12-13 at 11 27
39@2x](https://github.com/user-attachments/assets/7c7828c0-c5c7-4dc6-931e-722366d4f15a)

- Adds the Switch component
- Updates `Selected`, `Selectable` -> `ToggleState`, `Toggleable`
- Adds `checkbox` and `switch` functions to align better with other
elements in our layout system.

We decided not to merge Switch and Checkbox. However, in a followup I'll
introduce a Toggle or AnyToggle enum so we can update
`CheckboxWithLabel` -> `ToggleWithLabel` as this component will work
exactly the same with either a Checkbox or a Switch.

Release Notes:

- N/A

crates/git_ui/src/git_panel.rs

@@ -658,7 +658,7 @@ impl GitPanel {
     ) -> impl IntoElement {
         let id = id.to_proto() as usize;
         let checkbox_id = ElementId::Name(format!("checkbox_{}", id).into());
-        let is_staged = Selection::Selected;
+        let is_staged = ToggleState::Selected;
 
         h_flex()
             .id(id)