in py3.8+ the first asyncio.Task object is allocated with the same ID every time

This is a problem in anyio because TaskInfo's `__eq__` goes on to compare dead object IDs

```python
>>> async def current_task():
... return anyio.get_current_task()
...
>>> t = anyio.run(current_task)
>>> u = anyio.run(current_task)
>>> t == u
True
>>> t.id == u.id
True
```