tests/functional: Convert simple avocado tests into standalone python tests

tests/functional: Convert simple avocado tests into standalone python tests

These test are rather simple and don't need any modifications apart
from adjusting the "from avocado_qemu" line. To ease debugging, make
the files executable and add a shebang line and Python '__main__'
handling, too, so that these tests can now be run by executing them
directly.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20240830133841.142644-13-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>