The @ionic-native/google-maps is still member of the @ionic-native/google-maps.
You can use the @ionic-native/google-maps as well ad before.
The only difference is the code of the @ionic-native/google-maps is moved to new repository.
@ionic-native/google-maps works on ionic 3 and ionic 4.
If you want to use Google Maps in ionic 1, and ionic 2, you need to use cordova-plugin-googlemaps directly.
Unfortunately the plugin does not support Capacitor yet.