When an async Django middleware defines an `async def` hook such as
`process_view` or `process_exception`, the SDK wrapped it in a synchronous
function. That hid the coroutine from Django's `iscoroutinefunction` check in
`BaseHandler.load_middleware`, so Django wrapped the hook in `SyncToAsync` and
called it synchronously. The underlying coroutine was then never awaited, and
the request failed with:

```
ValueError: The view ... didn't return an HttpResponse object.
            It returned an unawaited coroutine instead.
```

`_get_wrapped_method` in the Django middleware integration now produces an
`async def` wrapper when the wrapped middleware hook is a coroutine function,
instead of always producing a synchronous wrapper.