AppState.currentState is always returning undefined in RNW 0.63.6

[shanelile]

My team is trying to upgrade to RNW 0.63, and I've noticed what looks like a regression in a component that relies on AppState from react-native, where AppState.currentState is always returning undefined.

Digging into the code, it looks like a possible regression from updating \node_modules\react-native-windows\Microsoft.ReactNative\Modules\AppStateModule.cpp - GetCurrentAppState returns a plain string, either "active" or "background". However, node_modules\react-native-windows\Libraries\AppState\AppState.js attempts to compare its currentState value to appStateData.app_state, which is not a valid field to reference.

[NickGerleman]

It does look like we changed the event shape in #4991 (FYI @acoates-ms). Seems like this should be simple to fix, and add an integration test for to make sure the JS library interacts correctly with our module (at least for the happy path of current active state).

0.63+ is impacted