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/with-variant/skip_ser_struct_field.stderr

@@ -0,0 +1,8 @@
+error: variant `Struct` cannot have both #[serde(serialize_with)] and a field `f1` marked with #[serde(skip_serializing)]
+  --> $DIR/skip_ser_struct_field.rs:12:10
+   |
+12 | #[derive(Serialize)]
+   |          ^^^^^^^^^
+
+error: aborting due to previous error
+