Move unit test compat code out of lib/ansible/. (#46996)

* Move ansible.compat.tests to test/units/compat/.
* Fix unit test references to ansible.compat.tests.
* Move builtins compat to separate file.
* Fix classification of test/units/compat/ dir.

test/units/plugins/inventory/test_group.py

@@ -15,7 +15,7 @@
 # You should have received a copy of the GNU General Public License
 # along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
 
-from ansible.compat.tests import unittest
+from units.compat import unittest
 
 from ansible.inventory.group import Group
 from ansible.inventory.host import Host

test/units/plugins/inventory/test_host.py

@@ -18,7 +18,7 @@
 # for __setstate__/__getstate__ tests
 import pickle
 
-from ansible.compat.tests import unittest
+from units.compat import unittest
 
 from ansible.inventory.group import Group
 from ansible.inventory.host import Host

test/units/plugins/inventory/test_inventory.py

@@ -23,8 +23,8 @@ import string
 import textwrap
 
 from ansible import constants as C
-from ansible.compat.tests import mock
-from ansible.compat.tests import unittest
+from units.compat import mock
+from units.compat import unittest
 from ansible.module_utils.six import string_types
 from ansible.module_utils._text import to_text
 from units.mock.path import mock_unfrackpath_noop

test/units/plugins/inventory/test_script.py

@@ -26,8 +26,8 @@ import pytest
 from ansible import constants as C
 from ansible.errors import AnsibleError
 from ansible.plugins.loader import PluginLoader
-from ansible.compat.tests import mock
-from ansible.compat.tests import unittest
+from units.compat import mock
+from units.compat import unittest
 from ansible.module_utils._text import to_bytes, to_native