Request always permission on Android

[siewedu]

Android 10 introduced the ACCESS_BACKGROUND_LOCATION permission. In order to ensure that the "always" option is presented to the user in the system dialog, we need to request for this permission specifically. See also https://github.com/NativeScript/nativescript-geolocation/issues/279

Since the always parameter is already defined for iOS we can also make use of it for the Android location request.