Fix broken handling of primitive items

- Fix broken handling of primitive associated items
- Remove fragment hack

  Fixes 83083

- more logging
- Update CrateNum hacks

  The CrateNum has no relation to where in the dependency tree the crate
  is, only when it's loaded. Explicitly special-case core instead of
  assuming it will be the first DefId.

- Update and add tests
- Cache calculation of primitive locations

  This could possibly be avoided by passing a Cache into
  collect_intra_doc_links; but that's a much larger change, and doesn't
  seem valuable other than for this.

src/librustdoc/json/conversions.rs

@@ -30,9 +30,7 @@ impl JsonRenderer<'_> {
             .get(&item.def_id)
             .into_iter()
             .flatten()
-            .filter_map(|clean::ItemLink { link, did, .. }| {
-                did.map(|did| (link.clone(), from_item_id(did.into())))
-            })
+            .map(|clean::ItemLink { link, did, .. }| (link.clone(), from_item_id((*did).into())))
             .collect();
         let docs = item.attrs.collapsed_doc_value();
         let attrs = item