gh-110529: Guard _testcapi imports in tests

Author: sobolevn

Lib/test/test_capi/test_abstract.py

@@ -1,6 +1,8 @@
 import unittest
 from collections import OrderedDict
-import _testcapi
+from test.support import import_helper
+
+_testcapi = import_helper.import_module('_testcapi')
 
 
 NULL = None

Lib/test/test_capi/test_dict.py

@@ -1,7 +1,9 @@
 import unittest
 from collections import OrderedDict, UserDict
 from types import MappingProxyType
-import _testcapi
+from test.support import import_helper
+
+_testcapi = import_helper.import_module('_testcapi')
 
 
 NULL = None