Expose UIManager from Scheduler (#33545)

Summary:
Pull Request resolved: #33545

Exposes `UIManager` instance for access from third-party modules.

Changelog: [Changed] Exposes `UIManager` instance for third-party access.

Reviewed By: javache

Differential Revision: D35314058

fbshipit-source-id: 1922c2afc37b105b153a82f45e5bac9c0b0cdfae

Author: cortinico

React/Fabric/RCTScheduler.h

@@ -16,6 +16,7 @@
 #import <react/renderer/mounting/MountingCoordinator.h>
 #import <react/renderer/scheduler/SchedulerToolbox.h>
 #import <react/renderer/scheduler/SurfaceHandler.h>
+#import <react/renderer/uimanager/UIManager.h>
 #import <react/utils/ContextContainer.h>
 
 NS_ASSUME_NONNULL_BEGIN
@@ -48,6 +49,7 @@ NS_ASSUME_NONNULL_BEGIN
 @interface RCTScheduler : NSObject
 
 @property (atomic, weak, nullable) id<RCTSchedulerDelegate> delegate;
+@property (readonly) std::shared_ptr<facebook::react::UIManager> const uiManager;
 
 - (instancetype)initWithToolbox:(facebook::react::SchedulerToolbox)toolbox;
 

React/Fabric/RCTScheduler.mm

@@ -203,4 +203,9 @@ - (void)removeEventListener:(std::shared_ptr<EventListener> const &)listener
   return _scheduler->removeEventListener(listener);
 }
 
+- (std::shared_ptr<facebook::react::UIManager> const)uiManager
+{
+  return _scheduler->getUIManager();
+}
+
 @end

ReactCommon/react/renderer/scheduler/Scheduler.cpp

@@ -368,6 +368,10 @@ ContextContainer::Shared Scheduler::getContextContainer() const {
   return contextContainer_;
 }
 
+std::shared_ptr<UIManager> Scheduler::getUIManager() const {
+  return uiManager_;
+}
+
 void Scheduler::addEventListener(
     const std::shared_ptr<EventListener const> &listener) {
   if (eventDispatcher_->has_value()) {

ReactCommon/react/renderer/scheduler/Scheduler.h

@@ -108,6 +108,9 @@ class Scheduler final : public UIManagerDelegate {
 #pragma mark - ContextContainer
   ContextContainer::Shared getContextContainer() const;
 
+#pragma mark - UIManager
+  std::shared_ptr<UIManager> getUIManager() const;
+
 #pragma mark - Event listeners
   void addEventListener(const std::shared_ptr<EventListener const> &listener);
   void removeEventListener(