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/utils/format_distance.rs

@@ -1,5 +1,4 @@
 // This won't be documented further as it is intended to be removed, or merged with the `time_format` crate.
-#![allow(missing_docs)]
 
 use chrono::{DateTime, Local, NaiveDateTime};
 

crates/ui/src/utils/search_input.rs

@@ -1,5 +1,3 @@
-#![allow(missing_docs)]
-
 use gpui::Pixels;
 
 pub struct SearchInputWidth;