This PR optimizes global object singleton creation by removing the getOrCreate() from the hot path for most of the global objects.

• getOrCreate() method locks mutex on every call
• We cannot just use the C++11 way of creating static singleton variables inside corresponding methods because we need to control the destruction order of global objects. Therefore, we use static variables to cache the result of the getOrCreate() method so that it calls only once per global object.
• The optimization is not done for the GlobalHandler::getPlatformToDefaultContextCache method because there are public methods of the GlobalHandler that can set the MPlatformToDefaultContextCache back to nullptr.