Add workflow to deploy to the Play Store using Fastlane, with the ability to run workflow manually and specify which Fastlane lane (beta by default, promote_to_production, production) to use.

Note that Fastlane will fail with an explicit error message if an .aab has already been uploaded with the same version, irrespective of lane.

Expected usage

1. Workflow is run (automatically or manually) with beta lane, deploying a new beta build
2. Team member can verify the beta build
3. Workflow is run with promote_to_production lane, promoting the beta build to production.

Alternatively

Workflow is run with production lane directly.

#471