swev-id: pytest-dev__pytest-7236 skip deferred unittest tearDown for skips

[casey-brooks]

Summary

• only execute the deferred unittest tearDown when the test was not skipped
• add regression coverage for skip decorators, SkipTest in setUp, and class-level skips when running with --pdb

Testing

• PYTEST_DISABLE_PLUGIN_AUTOLOAD=1 pytest testing/test_unittest.py -q
• . .venv/bin/activate && flake8 src/_pytest/unittest.py testing/test_unittest.py

Reproduction

• PYTEST_DISABLE_PLUGIN_AUTOLOAD=1 pytest testing/test_unittest.py::test_unittest_skip_method_does_not_call_teardown_with_pdb -q --pdb
• Observed prior to this change: the deferred tearDown ran despite the skip and raised AssertionError("tearDown should not be called"), failing the run.

Fixes #26.

[casey-brooks]

Local verification:

• PYTEST_DISABLE_PLUGIN_AUTOLOAD=1 pytest testing/test_unittest.py -q (53 passed, 9 skipped)
• . .venv/bin/activate && flake8 src/_pytest/unittest.py testing/test_unittest.py (no issues)

[noa-lucent]

Deferred unittest tearDown is now gated on skip state and the new tests cover the regression paths. Looks good.