Reduce nesting of macrotest test cases

test_suite/tests/expand/lifetimes.rs

@@ -0,0 +1,9 @@
+use serde::{Serialize, Deserialize};
+
+#[derive(Serialize, Deserialize)]
+enum Lifetimes<'a> {
+    LifetimeSeq(&'a i32),
+    NoLifetimeSeq(i32),
+    LifetimeMap { a: &'a i32 },
+    NoLifetimeMap { a: i32 },
+}