Change firebase-app-distribution-action to something more recent

From Kseniia:

nickwph/firebase-app-distribution-action is a 3rd party Action. The author hasn't updated it in three years - and I'm always a bit hesitant to add 3rd party Actions because they have access to the code and secrets in the workflow they are running inside of.

The Firebase CLI is pre-installed on our runners, so that's possible to use:
https://firebase.google.com/docs/app-distribution/android/distribute-cli?apptype=aab

Or uploading via Gradle:
https://firebase.google.com/docs/app-distribution/android/distribute-gradle?apptype=aab

We also have a repository of our own Q42 actions here. So it's also possible (if it requires a lot of YAML/code) to create a custom action that is shared across projects there:
https://github.com/Q42/actions

Locate the GitHub Actions workflow that invokes nickwph/firebase-app-distribution-action and read how the Android bundle is built and distributed. Compare the Firebase CLI and Gradle distribution approaches described in the linked documentation, while considering whether a shared Q42 action is needed. Done means the outdated third-party action is replaced and app distribution still works.