Wire shouldYield flag to a feature flag

Summary:
Changelog: [internal]

Add a feature flag to enable yielding in RuntimeScheduler

Reviewed By: JoshuaGross

Differential Revision: D28903226

fbshipit-source-id: c361ca144a2d531e8aa671bc8875bce075e13a2c

React/Fabric/RCTSurfacePresenter.mm

@@ -284,6 +284,8 @@ static BackgroundExecutor RCTGetBackgroundExecutor()
 
   if (reactNativeConfig && reactNativeConfig->getBool("react_fabric:enable_runtimescheduler_ios")) {
     auto runtimeScheduler = std::make_shared<RuntimeScheduler>(_runtimeExecutor);
+    runtimeScheduler->setEnableYielding(
+        reactNativeConfig->getBool("react_native_new_architecture:runtimescheduler_enable_yielding_ios"));
     toolbox.runtimeScheduler = runtimeScheduler;
     runtimeExecutor = [runtimeScheduler](std::function<void(jsi::Runtime & runtime)> &&callback) {
       runtimeScheduler->scheduleWork(std::move(callback));