support/testing: add python-cloudpickle tests

Add a basic runtime test for the python-cloudpickle package.
This test verifies the fundamental serialization capabilities of the
library by:
- Importing `cloudpickle`.
- Defining a simple Python function (fibonacci).
- Using `cloudpickle.dumps()` to serialize this function.

Signed-off-by: Xukai Wang <kingxukai@zohomail.com>
[Julien: fix flake8 warnings to fix check-package errors]
Signed-off-by: Julien Olivain <ju.o@free.fr>

support/testing/tests/package/test_python_cloudpickle.py

@@ -0,0 +1,12 @@
+from tests.package.test_python import TestPythonPackageBase
+
+
+class TestPythonPy3Cloudpickle(TestPythonPackageBase):
+    __test__ = True
+    config = TestPythonPackageBase.config + \
+        """
+        BR2_PACKAGE_PYTHON3=y
+        BR2_PACKAGE_PYTHON_CLOUDPICKLE=y
+        """
+    sample_scripts = ["tests/package/sample_python_cloudpickle.py"]
+    timeout = 20