gh-48330: assert warning is emitted on unittest.TestResult with no addDuration

[iritkatriel]

Fixes the warning below, which started with #12271.

====================================================================== ERROR: test_run_call_order_default_result (test.test_unittest.test_case.Test_TestCase.test_run_call_order_default_result) ---------------------------------------------------------------------- AttributeError: 'ResultWithNoStartTestRunStopTestRun' object has no attribute 'addDuration' During handling of the above exception, another exception occurred: Traceback (most recent call last): File "/Users/iritkatriel/src/cpython/Lib/test/test_unittest/test_case.py", line 307, in test_run_call_order_default_result Foo('test').run() File "/Users/iritkatriel/src/cpython/Lib/unittest/case.py", line 639, in run self._addDuration(result, (time.perf_counter() - start_time)) File "/Users/iritkatriel/src/cpython/Lib/unittest/case.py", line 580, in _addDuration warnings.warn("TestResult has no addDuration method", RuntimeWarning: TestResult has no addDuration method 

• Issue: unittest: display time used by each test case #48330

[giampaolo]

Thanks. LGTM.