Fix: Make RCTSurfacePresenter weakly retain its observers
Fix: Make RCTSurfacePresenter weakly retain its observers

Summary:
Changelog: [Fabric][iOS] Fix: Make RCTSurfacePresenter weakly retain its observers

There is retain cycle because RCTSurfacePresenter is keeping an array of  RCTSurfacePresenterObserver, which is strongly retaining the class that owns this RCTSurfacePresenter.

This diff makes RCTSurfacePresenter weakly retain observers instead.

Reviewed By: RSNara

Differential Revision: D35439589

fbshipit-source-id: ddc7813976b543de12af6173b2f1b31c69b043a8

janicduplessis/react-native,janicduplessis/react-native,facebook/react-native,janicduplessis/react-native,janicduplessis/react-native,facebook/react-native,javache/react-native,facebook/react-native,javache/react-native,javache/react-native,facebook/react-native,facebook/react-native,javache/react-native,javache/react-native,javache/react-native,facebook/react-native,janicduplessis/react-native,javache/react-native,janicduplessis/react-native,facebook/react-native,javache/react-native,janicduplessis/react-native,facebook/react-native,janicduplessis/react-native,facebook/react-native,javache/react-native