Fix stale layout when a child switches to display: contents after insertion (#58721)

Summary:
Pull Request resolved: #58721

Each node caches how many of its children use `display: contents` (`contentsChildrenCount_`, added in react/yoga#1726). The count is updated in `insertChild`, `removeChild`, `replaceChild` and `setChildren`, but not when the display of a child that is already attached changes.

So if `YGNodeStyleSetDisplay(child, YGDisplayContents)` is called after the child was inserted, the owner still reports `hasContentsChildren() == false`. The layout algorithm then skips `cleanupContentsNodesRecursively` for it, and the contents node keeps `isDirty == true` after layout. When a descendant of that node changes later, `markDirtyAndPropagate` stops at the contents node because it is already dirty, the root is never marked dirty, and the next `YGNodeCalculateLayout` returns the cached layout.

Minimal repro:

```cpp
YGNodeRef root = YGNodeNew();
YGNodeStyleSetWidth(root, 100);
YGNodeStyleSetHeight(root, 100);
YGNodeRef child = YGNodeNew();
YGNodeInsertChild(root, child, 0);
YGNodeRef grandchild = YGNodeNew();
YGNodeStyleSetWidth(grandchild, 10);
YGNodeStyleSetHeight(grandchild, 10);
YGNodeInsertChild(child, grandchild, 0);

YGNodeStyleSetDisplay(child, YGDisplayContents);
YGNodeCalculateLayout(root, YGUndefined, YGUndefined, YGDirectionLTR);
// YGNodeIsDirty(child) is still true

YGNodeStyleSetWidth(grandchild, 20);
// YGNodeIsDirty(root) is false
YGNodeCalculateLayout(root, YGUndefined, YGUndefined, YGDirectionLTR);
// YGNodeLayoutGetWidth(grandchild) is 10, expected 20
```

This affects any binding that mutates nodes in place (the JS and Java bindings both go through `YGNodeStyleSetDisplay`). Setting the display before inserting the child works, which is what the existing tests do.

The fix recomputes the owner's count in `YGNodeStyleSetDisplay` when a node that has an owner switches to or from `display: contents`.

Changelog: [General][Fixed] - Fix stale layout when a child switches to `display: contents` after being inserted

X-link: react/yoga#2028

Test Plan:
Added `dirty_propagation_through_child_set_to_display_contents` to `tests/YGDirtyMarkingTest.cpp`. Without the fix, all three of its assertions fail (the contents node stays dirty, the root is not marked dirty, and the grandchild keeps width 10). With the fix it passes.

Ran the full C++ suite (`unit_tests.bat`, MSVC 2022 + Ninja): 855 tests passed.

Checked formatting of the changed files with the repo's clang-format version (21.1.2): `clang-format --dry-run --Werror yoga/YGNodeStyle.cpp tests/YGDirtyMarkingTest.cpp` reports no changes.

Reviewed By: javache

Differential Revision: D122122520

Pulled By: cipolleschi

fbshipit-source-id: 79433cfb8112c9e8596f1ae604de56055860d814

Author: kwy404

packages/react-native/ReactCommon/yoga/yoga/YGNodeStyle.cpp

@@ -152,7 +152,16 @@ YGOverflow YGNodeStyleGetOverflow(const YGNodeConstRef node) {
 }
 
 void YGNodeStyleSetDisplay(const YGNodeRef node, const YGDisplay display) {
+  const bool wasContents =
+      resolveRef(node)->style().display() == Display::Contents;
   updateStyle<&Style::display, &Style::setDisplay>(node, scopedEnum(display));
+
+  // The owner caches how many of its children use display: contents, so it
+  // has to be recomputed when an attached child switches to or from it.
+  auto owner = resolveRef(node)->getOwner();
+  if (owner != nullptr && wasContents != (display == YGDisplayContents)) {
+    owner->setChildren(owner->getChildren());
+  }
 }
 
 YGDisplay YGNodeStyleGetDisplay(const YGNodeConstRef node) {