Expose EventEmitter::dispatchEvent APIs for all platforms (#41345)

Summary:
Pull Request resolved: #41345

## Changelog:
[Internal] -

This API was already accessible on the Android platform, now other platforms (C++) would benefit from having it available as well.

Arguably, it's perfectly fine to have it as public class members - based on empiric experience with the use case we have had.

Reviewed By: christophpurrer

Differential Revision: D51031340

fbshipit-source-id: 0426deede5d9e5c552c92f8a25d30fe2274a1941

packages/react-native/ReactCommon/react/renderer/core/EventEmitter.h

@@ -58,13 +58,6 @@ class EventEmitter {
 
   const SharedEventTarget& getEventTarget() const;
 
- protected:
-#ifdef ANDROID
-  // We need this temporarily due to lack of Java-counterparts for particular
-  // subclasses.
- public:
-#endif
-
   /*
    * Initiates an event delivery process.
    * Is used by particular subclasses only.