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/snippets_ui/src/snippets_ui.rs

@@ -219,7 +219,7 @@ impl PickerDelegate for ScopeSelectorDelegate {
             ListItem::new(ix)
                 .inset(true)
                 .spacing(ListItemSpacing::Sparse)
-                .selected(selected)
+                .toggle_state(selected)
                 .child(HighlightedLabel::new(label, mat.positions.clone())),
         )
     }