ui: Update Label component (#24653)

- Standardize style methods
- Convert label story to a component preview
- update component preview styles  

Release Notes:

- N/A

crates/image_viewer/src/image_viewer.rs

@@ -131,7 +131,7 @@ impl Item for ImageView {
         Label::new(title)
             .single_line()
             .color(label_color)
-            .italic(params.preview)
+            .when(params.preview, |this| this.italic())
             .into_any_element()
     }