run-tests: store last result in Test._result Subsequent patches move post-test actions into tearDown(). This requires tearDown() to have access to the last result.

run-tests: report test duration in Test.tearDown()

run-tests: store test return code and output in Test instance A subsequent patch that will introduce tearDown() requires test execution state be stored in the instance.

run-tests: keep track of test start and stop in MercurialTest.run() This brings run() more compatible with unittest.TestCase.run()