Set `sys.last_exc` in addition to `last_type`/`last_value`/`last_traceback` on Python>=3.12

Python 3.12 added [`sys.last_exc`](https://docs.python.org/3/library/sys.html#sys.last_exc). We should set it [like we do the older variants](https://github.com/pytest-dev/pytest/blob/c3fc717ff74cb8be6fb04c630b28b720d6c041ad/src/_pytest/runner.py#L166-L181).