next_event_async might block Drop'ing the node #39
Description
If I have an application where I want to Drop the node (eg to reset the state and possibly create a new one), having a background loop running next_event_async is going to result in that not being possible. Its not really a huge deal because that just means the old node object will leak, but its kinda awkward. Either having a timeout on next_event_async (using tokio, I guess) so that exiting can happen, or letting it return Option<Event> and returning None immediately on stop() would suffice.
Similar to lightningdevkit/ldk-node#731