gpui: Fix intra rustdoc links (#37320)

The only warnings remaining are links to private modules/items, but I
lack knowledge to work out if the referenced modules/items should be
made public, or if the links should be rewritten into exposed
traits/items.

Links to associated items such as trait implementations have to be
written using full markdown format such as:

... [[ `App::update_global` ]](( BorrowAppContext::update_global ))

This is due to https://github.com/rust-lang/rust/issues/74563 which
sadly prohibits fully-qualified syntax:

... [[ `<App as BorrowAppContext>::update_global` ]]

Release Notes:

- N/A

Probably related to https://github.com/zed-industries/zed/pull/37072

crates/gpui/src/path_builder.rs

@@ -318,7 +318,7 @@ impl PathBuilder {
         Ok(Self::build_path(buf))
     }
 
-    /// Builds a [`Path`] from a [`lyon::VertexBuffers`].
+    /// Builds a [`Path`] from a [`lyon::tessellation::VertexBuffers`].
     pub fn build_path(buf: VertexBuffers<lyon::math::Point, u16>) -> Path<Pixels> {
         if buf.vertices.is_empty() {
             return Path::new(Point::default());