Add explicit orthogonal span sizing

tests/generated.rs

@@ -190,9 +190,10 @@ fn describe(id: WidgetId, h: &Harness) -> String {
     if let Some(w) = any.downcast_ref::<Span>() {
         let sign = if w.dir.sign == Sign::Neg { "-" } else { "+" };
         return format!(
-            "Span{{dir:{:?}{sign},gap:{},n:{}}}",
+            "Span{{dir:{:?}{sign},gap:{},ortho:{:?},n:{}}}",
             w.dir.axis,
             w.gap,
+            w.ortho,
             w.children.len()
         );
     }