Change AsyncStorage on client to mmkv storage

[J-467]

mmkv storage encrypts the data stored

mmkv: https://github.com/ammarahm-ed/react-native-mmkv-storage

[J-467]

Currently, we're are using AsyncStorage to store some user data on the client side. Think of user information, how many points they have etc. Think of it as caching on the client side, so they can retrieve it in instances of no connection to the database.

However AsyncStorage is deprecated and the data is unencrypted.