Improve the release app archive tests

See https://github.com/aboutcode-org/scancode-toolkit/issues/4469#issuecomment-3102849523 where we have a broken app archive. We have a temporary fix for this but to improve the release tests and ensure this doesn't happen in the future we need to:

- Move the unzipping archive steps inside the python script rather than in the CI script as this is much cleaner, fail loudly if this does not work
- Check if we actually found an app archive and fail loudly if we don't or if the release archive tests are not run for any reason