Summary:
The `getAllSharedPreferences` API is not implemented in the iOS UserDefaultsPlugin and thus the data is not shown in the `Shared Preference Viewer`.
This PR implements the missing API and present the Standard UserDefaults data from the target application.
Pull Request resolved: https://github.com/facebook/flipper/pull/340
Reviewed By: danielbuechele
Differential Revision: D13464765
Pulled By: priteshrnandgaonkar
fbshipit-source-id: 8c6cf4e9f7094fcf75c71cce43cb6c34f9f957e7
d7ecd3af5a