Run all timers in the main thread with epoll

This ditches 1+ threads in all use cases.

Change-Id: I8772a539c20cd10d80a57f3f53c48a3d8124461a
diff --git a/aos/events/simulated-event-loop.h b/aos/events/simulated-event-loop.h
index 6ee7d92..81b181f 100644
--- a/aos/events/simulated-event-loop.h
+++ b/aos/events/simulated-event-loop.h
@@ -120,6 +120,8 @@
     is_running_ = false;
   }
 
+  bool is_running() const { return is_running_; }
+
   void AddRawEventLoop(RawEventLoop *event_loop) {
     raw_event_loops_.push_back(event_loop);
   }