Improve several aspects of the Rustdoc scrape-examples UI.

* Examples take up less screen height.
* Snippets from binary crates are prioritized.
* toggle-all-docs does not expand "More examples" sections.

src/librustdoc/html/render/mod.rs

@@ -2957,14 +2957,22 @@ fn render_call_locations(w: &mut Buffer, cx: &mut Context<'_>, item: &clean::Ite
 
     // The call locations are output in sequence, so that sequence needs to be determined.
     // Ideally the most "relevant" examples would be shown first, but there's no general algorithm
-    // for determining relevance. Instead, we prefer the smallest examples being likely the easiest to
-    // understand at a glance.
+    // for determining relevance. We instead make a proxy for relevance with the following heuristics:
+    //   1. Code written to be an example is better than code not written to be an example, e.g.
+    //      a snippet from examples/foo.rs is better than src/lib.rs. We don't know the Cargo directory
+    //      structure in Rustdoc, so we proxy this by prioriting code that comes from a --crate-type bin.
+    //   2. Smaller examples are better than large examples. So we prioritize snippets that have the
+    //      smallest line span for their enclosing item.
+    //   3. Finally we sort by the displayed file name, which is arbitrary but prevents the ordering
+    //      of examples from randomly changing between Rustdoc invocations.
     let ordered_locations = {
-        let sort_criterion = |(_, call_data): &(_, &CallData)| {
+        fn sort_criterion<'a>(
+            (_, call_data): &(&PathBuf, &'a CallData),
+        ) -> (bool, u32, &'a String) {
             // Use the first location because that's what the user will see initially
             let (lo, hi) = call_data.locations[0].enclosing_item.byte_span;
-            hi - lo
-        };
+            (!call_data.is_bin, hi - lo, &call_data.display_name)
+        }
 
         let mut locs = call_locations.iter().collect::<Vec<_>>();
         locs.sort_by_key(sort_criterion);