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.

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