Properly handle reexport of foreign items.

Handles `pub use` of `extern { fn, static, type }`. Also plug in some more
`match` arms where handling `extern type` is reasonable.

Fixed #46098.

src/librustdoc/clean/mod.rs

@@ -2970,6 +2970,7 @@ fn register_def(cx: &DocContext, def: Def) -> DefId {
         Def::Struct(i) => (i, TypeKind::Struct),
         Def::Union(i) => (i, TypeKind::Union),
         Def::Mod(i) => (i, TypeKind::Module),
+        Def::TyForeign(i) => (i, TypeKind::Foreign),
         Def::Static(i, _) => (i, TypeKind::Static),
         Def::Variant(i) => (cx.tcx.parent_def_id(i).unwrap(), TypeKind::Enum),
         Def::SelfTy(Some(def_id), _) => (def_id, TypeKind::Trait),