EventLoop: add public wakeup() method, and call it from call()

call(), when invoked from the logic thread, wasn't triggering a wakeup
which stalled some traffic (such as client-to-snode packets).

Fix it by triggering a wakeup on `call()`, and expose it because this is
a useful thing to be able to do.

llarp/ev/ev.hpp

@@ -77,6 +77,12 @@ namespace llarp
       return llarp::time_now_ms();
     }
 
+    // Triggers an event loop wakeup; use when something has been done that requires the event loop
+    // to wake up (e.g. adding to queues).  This is called implicitly by call() and call_soon().
+    // Idempotent and thread-safe.
+    virtual void
+    wakeup() = 0;
+
     // Calls a function/lambda/etc.  If invoked from within the event loop itself this calls the
     // given lambda immediately; otherwise it passes it to `call_soon()` to be queued to run at the
     // next event loop iteration.
@@ -85,7 +91,10 @@ namespace llarp
     call(Callable&& f)
     {
       if (inEventLoop())
+      {
         f();
+        wakeup();
+      }
       else
         call_soon(std::forward<Callable>(f));
     }

llarp/ev/ev_libuv.cpp

@@ -149,6 +149,12 @@ namespace llarp::uv
     llarp::LogInfo("we have stopped");
   }
 
+  void
+  Loop::wakeup()
+  {
+    m_WakeUp->send();
+  }
+
   void
   Loop::set_pump_function(std::function<void(void)> pump)
   {

llarp/ev/ev_libuv.hpp

@@ -32,6 +32,9 @@ namespace llarp::uv
     bool
     running() const override;
 
+    void
+    wakeup() override;
+
     void
     call_later(llarp_time_t delay_ms, std::function<void(void)> callback) override;