Add tests for `org.beeware.ARGV` and `org.beeware.ENVIRON`

### What is the problem or limitation you are having?

Currently the command line arguments (passed to an android app via `org.beeware.ARGV`) and environment variables (passed to an android app via `org.beeware.ENVIRON` as proposed [here](https://github.com/beeware/briefcase-android-gradle-template/pull/97) ) are not automatically tested for android.

### Describe the solution you'd like

The command line arguments and environment variables should be automatically tested.

### Describe alternatives you've considered

Do not test these cases automatically. Manual testing is enough.

### Additional context

This has been proposed here: https://github.com/beeware/briefcase-android-gradle-template/pull/97#issuecomment-2767555341

Review the Android test setup in Python-support-testbed and the proposed changes in briefcase-android-gradle-template PR #97. Run the existing Android tests, then add automated coverage showing that org.beeware.ARGV and org.beeware.ENVIRON are passed into the app correctly. Done means both cases run automatically and pass.

Written by the indexing model from the issue text.