rename app distribution APK on upload

## What feature would you like to see?

The app distribution gradle plugin should let testers download APKs with the same file name as when they were uploaded

Testers can currently only download files named "app.apk" no matter the name of the apk file that was originally uploaded

Using the "artifactPath" parameter in gradle is a problem when the Android application has more than one build variant.

Could we add a "artifactName"?

## How would you use it?

This would let us keep meaningful names of APKs when distributing them from developers to testers. It would allow us to avoid mistakes when testing our mobile application

Both Jenkins and Gitlab let us control the name of the artifacts. We would like Firebase App Distribution to be our source of truth instead.