Fix unsafe downcasting in ShadowTree::emitLayoutEvents (#44058)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/44058

## Changelog:
[Internal] -

This was revealed when running an ASAN build on MacOS - we were doing an unsafe downcast from `LayoutableShadowNode->ViewShadowNode` inside `ShadowTree::emitLayoutEvents`.

Which, even though incidentally worked, is generally unsafe, as we may get e.g. `ImageShadowNode` there, which doesn't inherit from `ViewShadowNode`.

That downcast to `ViewShadowNode` wasn't even required, to begin with, as all the needed information can be already extracted from the `LayoutableShadowNode` itself.

Reviewed By: christophpurrer, javache

Differential Revision: D56062334

fbshipit-source-id: 08d5b3f5e0c57dc51b051d23506c7933581fea29

packages/react-native/ReactCommon/react/renderer/mounting/ShadowTree.cpp

@@ -575,15 +575,14 @@ void ShadowTree::emitLayoutEvents(
 
   for (const auto* layoutableNode : affectedLayoutableNodes) {
     // Only instances of `ViewShadowNode` (and subclasses) are supported.
-    const auto& viewShadowNode =
-        static_cast<const ViewShadowNode&>(*layoutableNode);
-    const auto& viewEventEmitter =
-        static_cast<const ViewEventEmitter&>(*viewShadowNode.getEventEmitter());
+
+    const auto& viewEventEmitter = static_cast<const BaseViewEventEmitter&>(
+        *layoutableNode->getEventEmitter());
 
     // Checking if the `onLayout` event was requested for the particular Shadow
     // Node.
     const auto& viewProps =
-        static_cast<const ViewProps&>(*viewShadowNode.getProps());
+        static_cast<const BaseViewProps&>(*layoutableNode->getProps());
     if (!viewProps.onLayout) {
       continue;
     }