RuntimeInitializeOnLoadMethod の型を設定します。
| AfterSceneLoad | After Scene is loaded. |
| BeforeSceneLoad | Before Scene is loaded. |
| AfterAssembliesLoaded | Callback when all assemblies are loaded and preloaded assets are initialized. |
| BeforeSplashScreen | Immediately before the splash screen is shown. |
| SubsystemRegistration | Callback used for registration of subsystems |