Derive icon paths (#17816)

This PR improves adding and working with icons by using the new
`DerivePathStr` to derive icon paths.

This means paths no longer need to be manually specified, and the
`IconName` and file name will always be consistent between icons.

This PR does not do any work to standardize icons visually, remove
unused icons, or any other such cleanup.

Release Notes:

- N/A

crates/ui/src/components/stories/list_header.rs

@@ -24,7 +24,7 @@ impl Render for ListHeaderStory {
             .child(
                 ListHeader::new("Section 4")
                     .end_slot(IconButton::new("action_1", IconName::Bolt))
-                    .end_slot(IconButton::new("action_2", IconName::ExclamationTriangle))
+                    .end_slot(IconButton::new("action_2", IconName::Warning))
                     .end_slot(IconButton::new("action_3", IconName::Plus)),
             )
     }