Enable layout animations on iOS in OSS

Summary:
changelog: Enable Layout Animations on iOS

[LayoutAnimations](https://reactnative.dev/docs/next/layoutanimation) in New Architecture have been disabled in OSS on iOS because of unresolved crash. This crash only happens rarely. Turning on LayoutAnimations in OSS should be safe and brings New Architecture to parity with old.

Reviewed By: fkgozali

Differential Revision: D42708774

fbshipit-source-id: b0f7febee3aa4f0ddac25556644198ebe79378c1

ReactCommon/react/config/ReactNativeConfig.cpp

@@ -21,6 +21,9 @@ ReactNativeConfig::~ReactNativeConfig() {}
 EmptyReactNativeConfig::EmptyReactNativeConfig() {}
 
 bool EmptyReactNativeConfig::getBool(const std::string &param) const {
+  if (param == "react_fabric:enabled_layout_animations_ios") {
+    return true;
+  }
   return false;
 }
 

ReactCommon/react/config/ReactNativeConfig.h

@@ -28,7 +28,7 @@ class ReactNativeConfig {
 };
 
 /**
- * Empty configuration that will always provide "falsy" values.
+ * Empty configuration that will provide hardcoded values.
  */
 class EmptyReactNativeConfig : public ReactNativeConfig {
  public:

ReactCommon/react/utils/ContextContainer.h

@@ -38,7 +38,7 @@ class ContextContainer final {
    * example if the type `T` is `std::shared_ptr<const ReactNativeConfig>`,
    * then one would use `"ReactNativeConfig"` for the `key`, even if the
    * instance is actually a `shared_ptr` of derived class
-   *`EmptyReactNativeConfig`.
+   *`ReactNativeConfig`.
    */
   template <typename T>
   void insert(std::string const &key, T const &instance) const {