Support setUpClass & tearDownClass with instantiate_device_type_tests() (#121686)
Summary: instantiate_device_type_tests() creates dynamic test case classes that derive from a "template class". By default, the test harness will call the setUpClass() and tearDownClass() methods defined by the template class (if the template class defines them). We can explicitly create these methods in the dynamic class and arrange to call those methods in both base classes. That allows us to support setUpClass & tearDownClass test classes used with instantiate_device_type_tests().
Pull Request resolved: https://github.com/pytorch/pytorch/pull/121686
Approved by: https://github.com/ezyang, https://github.com/eellison
