pub fn shutdown_tokio_runtime(py: Python<'_>)Expand description
atexit handler that tears down the global Tokio runtime.
Callers obtain a cloned Handle from get_tokio_runtime() rather
than a guard, so the runtime mutex is uncontended at shutdown. We
can take ownership of the Runtime and call shutdown_timeout
directly. If a worker thread is still inside Handle::block_on on a
future that never resolves (e.g. a non-main thread that cannot
observe SIGINT), shutdown_timeout aborts spawned tasks and returns
after at most one second; the stuck worker is then a daemon thread
that CPython kills on interpreter exit.