ui: More component previews, UI component cleanup (#25302)

- Don't require ui component docs (this isn't really working)
- Add more component previews
- Update component preview style & navigation

Release Notes:

- N/A

crates/ui/src/components/numeric_stepper.rs

@@ -1,5 +1,3 @@
-#![allow(missing_docs)]
-
 use gpui::ClickEvent;
 
 use crate::{prelude::*, IconButtonShape};