UDP for RAK4631 Eth Gw and the t-eth-elite. Solves #7149 (#7385)

* UDP for RAK4631 Eth Gw and the t-eth-elite. Also enable IP output on Portduino. Solves #7149

* Copilot suggestion

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* fix portduino build

* initialize local port

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Ben Meadors <benmmeadors@gmail.com>

src/platform/nrf52/AsyncUDP.cpp

@@ -0,0 +1,69 @@
+#include "AsyncUDP.h"
+
+AsyncUDP::AsyncUDP() : OSThread("AsyncUDP"), localPort(0) {}
+
+bool AsyncUDP::listenMulticast(IPAddress multicastIP, uint16_t port, uint8_t ttl)
+{
+    if (!isMulticast(multicastIP))
+        return false;
+    localPort = port;
+    udp.beginMulticast(multicastIP, port);
+    return true;
+}
+
+size_t AsyncUDP::write(uint8_t b)
+{
+    return udp.write(&b, 1);
+}
+
+size_t AsyncUDP::write(const uint8_t *data, size_t len)
+{
+    return udp.write(data, len);
+}
+
+void AsyncUDP::onPacket(const std::function<void(AsyncUDPPacket)> &callback)
+{
+    _onPacket = callback;
+}
+
+bool AsyncUDP::writeTo(const uint8_t *data, size_t len, IPAddress ip, uint16_t port)
+{
+    if (!udp.beginPacket(ip, port))
+        return false;
+    udp.write(data, len);
+    return udp.endPacket();
+}
+
+// AsyncUDPPacket
+AsyncUDPPacket::AsyncUDPPacket(EthernetUDP &source) : _udp(source), _remoteIP(source.remoteIP()), _remotePort(source.remotePort())
+{
+    if (_udp.available() > 0) {
+        _readLength = _udp.read(_buffer, sizeof(_buffer));
+    } else {
+        _readLength = 0;
+    }
+}
+
+IPAddress AsyncUDPPacket::remoteIP()
+{
+    return _remoteIP;
+}
+
+uint16_t AsyncUDPPacket::length()
+{
+    return _readLength;
+}
+
+const uint8_t *AsyncUDPPacket::data()
+{
+    return _buffer;
+}
+
+int32_t AsyncUDP::runOnce()
+{
+    if (_onPacket && udp.parsePacket() > 0) {
+        AsyncUDPPacket packet(udp);
+        _onPacket(packet);
+    }
+    return 5; // check every 5ms
+}