Move all compile-fail tests to ui tests

The update-references.sh script makes these much easier to update in
bulk compared to compile-fail tests.

test_suite/tests/ui/borrow/struct_variant.stderr

@@ -0,0 +1,8 @@
+error: #[serde(borrow)] may only be used on newtype variants
+  --> $DIR/struct_variant.rs:15:10
+   |
+15 | #[derive(Deserialize)]
+   |          ^^^^^^^^^^^
+
+error: aborting due to previous error
+