Skip non-owned subtrees in roundLayoutResultsToPixelGrid (#2015)

Summary:
Pull Request resolved: #2015

> [!NOTE]
> **This PR description is AI-generated.**

Fabric runs layout on candidate trees before taking the commit mutex, and concurrent commits share every unchanged subtree, so Yoga's pixel-grid rounding pass could write rounded positions and dimensions into the same shared `yoga::Node` from two threads at once. The layout pass itself never mutates nodes it does not own (`Node::cloneChildrenIfNeeded`), but `roundLayoutResultsToPixelGrid` recursed across the ownership frontier. I made the rounding recursion skip children whose owner is not the current node, mirroring the existing owner checks in `Node::cloneChildrenIfNeeded` and `YGNodeFreeRecursive`. The skipped writes had no reader: `YogaLayoutableShadowNode::layout` copies metrics only from children with `hasNewLayout` (asserting they are owned), `hasNewLayout` is set only on nodes the pass laid out, and the shadow nodes past the frontier are sealed, so their `LayoutMetrics` could not change in that commit anyway.

## Changelog:

[GENERAL] [FIXED] - Fix data race between concurrent Fabric commits in Yoga's pixel-grid rounding pass

X-link: react/react-native#58144

Test Plan: ThreadSanitizer reports of the race, from react-native-reanimated's sanitizer nightly (React commit on the JS thread racing a Reanimated commit on the main thread over a shared `ParagraphShadowNode`): https://github.com/software-mansion/react-native-reanimated/actions/runs/32811464205/job/97691453444

Reviewed By: christophpurrer

Differential Revision: D117688567

Pulled By: zeyap

fbshipit-source-id: 3f0662aee2ce865b4a13edffd46217f349a4285d

Author: tjzel

yoga/algorithm/PixelGrid.cpp

@@ -128,6 +128,9 @@ void roundLayoutResultsToPixelGrid(
   }
 
   for (yoga::Node* child : node->getChildren()) {
+    if (child->getOwner() != node) {
+      continue;
+    }
     roundLayoutResultsToPixelGrid(child, absoluteNodeLeft, absoluteNodeTop);
   }
 }