Use locale insensitive toUpperCase and toLowerCase

[kyo504]

Fixes # #728

Test Plan:

Before this PR, if you run following example,

export default class App extends Component<{}> {
  _login = async () => {
    try {
      LoginManager.setLoginBehavior('native_with_fallback');
      await LoginManager.logInWithPermissions(['email']);
    } catch (e) {
      Alert.alert(JSON.stringify(e));
    }
  };

  render() {
    return (
      <View style={styles.container}>
        <TouchableHighlight onPress={this._login}>
          <Text>Login</Text>
        </TouchableHighlight>
      </View>
    );
  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
    backgroundColor: '#F5FCFF',
  },
});

you could see the following error on Android Debug Console.

E/unknown:ReactNative: Exception in native call
    java.lang.IllegalArgumentException: No enum constant com.facebook.login.LoginBehavior.NATİVE_WİTH_FALLBACK
        at java.lang.Enum.valueOf(Enum.java:258)
        at com.facebook.login.LoginBehavior.valueOf(LoginBehavior.java:26)
        at com.facebook.reactnative.androidsdk.FBLoginManagerModule.setLoginBehavior(FBLoginManagerModule.java:100)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.facebook.react.bridge.JavaMethodWrapper.invoke(JavaMethodWrapper.java:372)
        at com.facebook.react.bridge.JavaModuleWrapper.invoke(JavaModuleWrapper.java:158)
        at com.facebook.react.bridge.queue.NativeRunnable.run(Native Method)
        at android.os.Handler.handleCallback(Handler.java:873)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at com.facebook.react.bridge.queue.MessageQueueThreadHandler.dispatchMessage(MessageQueueThreadHandler.java:29)
        at android.os.Looper.loop(Looper.java:193)
        at com.facebook.react.bridge.queue.MessageQueueThreadImpl$4.run(MessageQueueThreadImpl.java:232)
        at java.lang.Thread.run(Thread.java:764)

And this leads crash on release mode. I've tested that app works fine after this pr.

[mifi]

Maybe better to not use a case transformation for such keys at all and instead replace it with a more robust transformation logic?

[kyo504]

@mifi yeah, that would be another way to solve this problem. But I don't know the history of current implementation and what you mentioned would cause backward compatibility issue(I think this is not as important as all the people should bump major version).

[janicduplessis]

I agree with @mifi, can we use a switch statement to return the proper enum value instead?