[cdc_stream] Add integration tests (#44)

This CL adds Python integration tests for cdc_stream. To run the
tests, you need to supply a Linux host and proper configuration for
cdc_stream to work:

set CDC_SSH_COMMAND=C:\path\to\ssh.exe <args>
set CDC_SCP_COMMAND=C:\path\to\scp.exe <args>
C:\python38\python.exe -m integration_tests.cdc_stream.all_tests --binary_path=C:\full\path\to\cdc_stream.exe --user_host=user@host

Ran the tests and made sure they worked.

integration_tests/cdc_stream/all_tests.py

@@ -0,0 +1,42 @@
+# Copyright 2022 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Lint as: python3
+import unittest
+
+from integration_tests.cdc_stream import cache_test
+from integration_tests.cdc_stream import consistency_test
+from integration_tests.cdc_stream import directory_test
+from integration_tests.cdc_stream import general_test
+from integration_tests.framework import test_base
+
+
+# pylint: disable=g-doc-args,g-doc-return-or-yield
+def load_tests(loader, unused_tests, unused_pattern):
+  """Customizes the list of test cases to run.
+
+  See the Python documentation for details:
+  https://docs.python.org/3/library/unittest.html#load-tests-protocol
+  """
+  suite = unittest.TestSuite()
+  suite.addTests(loader.loadTestsFromModule(cache_test))
+  suite.addTests(loader.loadTestsFromModule(consistency_test))
+  suite.addTests(loader.loadTestsFromModule(directory_test))
+  suite.addTests(loader.loadTestsFromModule(general_test))
+
+  return suite
+
+
+if __name__ == '__main__':
+  test_base.main()