Add more missing methods to IntraLinkCrateLoader

This helps with (but does not fix)
https://github.com/rust-lang/rust/issues/84738. I tested on
edcee7b812
and still hit ICEs.

src/test/rustdoc-ui/intra-doc/auxiliary/dep1.rs

@@ -0,0 +1 @@
+// intentionally empty

src/test/rustdoc-ui/intra-doc/auxiliary/dep2.rs

@@ -0,0 +1 @@
+// intentionally empty

src/test/rustdoc-ui/intra-doc/auxiliary/dep3.rs

@@ -0,0 +1 @@
+// intentionally empty

src/test/rustdoc-ui/intra-doc/auxiliary/dep4.rs

@@ -0,0 +1 @@
+// intentionally empty

src/test/rustdoc-ui/intra-doc/extern-crate-load.rs

@@ -0,0 +1,26 @@
+// check-pass
+// aux-crate:dep1=dep1.rs
+// aux-crate:dep2=dep2.rs
+// aux-crate:dep3=dep3.rs
+// aux-crate:dep4=dep4.rs
+#![deny(rustdoc::broken_intra_doc_links)]
+
+pub trait Trait {
+    /// [dep1]
+    type Item;
+}
+
+pub struct S {
+    /// [dep2]
+    pub x: usize,
+}
+
+extern "C" {
+    /// [dep3]
+    pub fn printf();
+}
+
+pub enum E {
+    /// [dep4]
+    A
+}