Fix late load of anyio doing blocking I/O in the event loop (#114491)

* Fix late load of anyio doing blocking I/O in the event loop

httpx loads anyio which loads the asyncio backend in the event loop
as soon as httpx makes the first request

* tweak

homeassistant/bootstrap.py

@@ -93,6 +93,11 @@ from .util.async_ import create_eager_task
 from .util.logging import async_activate_log_queue_handler
 from .util.package import async_get_user_site, is_virtual_env
 
+with contextlib.suppress(ImportError):
+    # Ensure anyio backend is imported to avoid it being imported in the event loop
+    from anyio._backends import _asyncio  # noqa: F401
+
+
 if TYPE_CHECKING:
     from .runner import RuntimeConfig