feat(mqtt): enhance neighbor discovery with request management

Add functionality to manage neighbor discovery requests in MyMesh.
This includes handling the status of requests, updating the state
upon transmission success or failure, and implementing a timeout
mechanism for neighbor discovery queries. The changes improve the
efficiency and reliability of neighbor discovery operations in
MQTT-enabled environments.

src/Dispatcher.h

@@ -213,6 +213,7 @@ public:
   uint32_t getNumRecvDirect() const { return n_recv_direct; }
   uint16_t getErrFlags() const { return _err_flags; }  // Get error flags
   bool hasOutbound() const { return outbound != NULL; }
+  bool isCurrentOutbound(const Packet* packet) const { return outbound == packet; }
   void resetStats() {
     n_sent_flood = n_sent_direct = n_recv_flood = n_recv_direct = 0;
     _err_flags = 0;