pretty: print attrs in struct expr

src/test/pretty/issue-68710-field-attr-proc-mac-lost.rs

@@ -0,0 +1,16 @@
+// pp-exact
+
+fn main() { }
+
+struct C {
+    field: u8,
+}
+
+#[allow()]
+const C: C =
+    C{
+      #[cfg(debug_assertions)]
+      field: 0,
+
+      #[cfg(not (debug_assertions))]
+      field: 1,};