make certbot tests internal (#9627)

This is the Certbot version of https://github.com/certbot/certbot/pull/9625.

certbot/MANIFEST.in

@@ -4,7 +4,6 @@ include LICENSE.txt
 recursive-include docs *
 recursive-include examples *
 recursive-include certbot/tests/testdata *
-recursive-include tests *.py
 include certbot/ssl-dhparams.pem
 include certbot/py.typed
 global-exclude __pycache__

certbot/certbot/_internal/tests/__init__.py

@@ -0,0 +1 @@
+"""certbot tests"""

certbot/certbot/_internal/tests/cert_manager_test.py

@@ -14,11 +14,11 @@ import pytest
 from certbot import configuration
 from certbot import errors
 from certbot._internal.storage import ALL_FOUR
+from certbot._internal.tests import storage_test
 from certbot.compat import filesystem
 from certbot.compat import os
 from certbot.display import util as display_util
 from certbot.tests import util as test_util
-import storage_test
 
 
 class BaseCertManagerTest(test_util.ConfigTestCase):