sm: Relocate the service manager to the System class

Rather than have it live as a global variable, place it into the System class and make it instance-based.

src/core/hle/service/service.h

@@ -262,7 +262,7 @@ private:
 };
 
 /// Initialize ServiceManager
-void Init();
+void Init(std::shared_ptr<SM::ServiceManager>& sm);
 
 /// Shutdown ServiceManager
 void Shutdown();