[Android] Specify a namespace

[fdrault]

React Native 0.73 will depend on Android Gradle Plugin (AGP) 8.x. This will require all the libraries to specify a namespace in their build.gradle file. We added a compatibility layer for libraries that haven't specified a namespace, but please consider updating your libraries nonetheless.

To follow last recommandation, we need to specify a namespace for our library. It will breaks compatibility with RN<71, so I might wait a bit before comply to this.

Note: react-native-community/discussions-and-proposals#671