Add UDP transport with picomap port 28781, info -udp flag

firmware/include/net.h

@@ -1,12 +1,18 @@
 #pragma once
 #include <array>
 #include <cstdint>
+#include <functional>
+#include <span>
+#include <vector>
 
 struct net_state {
     std::array<uint8_t, 6> mac;
     std::array<uint8_t, 4> ip;
 };
 
+using net_handler = std::function<std::vector<std::vector<uint8_t>>(std::span<const uint8_t> payload)>;
+
 bool net_init();
 const net_state& net_get_state();
+void net_set_handler(net_handler handler);
 void net_poll();