Reduce nesting of macrotest test cases

test_suite/tests/expand/generic_struct.rs

@@ -0,0 +1,9 @@
+use serde::{Serialize, Deserialize};
+
+#[derive(Serialize, Deserialize)]
+pub struct GenericStruct<T> {
+    x: T,
+}
+
+#[derive(Serialize, Deserialize)]
+pub struct GenericNewTypeStruct<T>(T);