feat(udp): Allow to change the async_udp task stack size

Example:  `-D CONFIG_ARDUINO_UDP_TASK_STACK_SIZE=2048`
The default is to much conservative since a correctly developed app probably won't allocate too much on stack on the callbacks. I currently see a wast of memory:
`I (1222501) MONITOR: async_udp  (p=3) 3416 bytes`

Author: mathieucarbou

libraries/AsyncUDP/src/AsyncUDP.cpp

@@ -15,6 +15,10 @@ extern "C" {
 
 #include "lwip/priv/tcpip_priv.h"
 
+#ifndef CONFIG_ARDUINO_UDP_TASK_STACK_SIZE
+#define CONFIG_ARDUINO_UDP_TASK_STACK_SIZE 4096
+#endif
+
 #ifdef CONFIG_LWIP_TCPIP_CORE_LOCKING
 #define UDP_MUTEX_LOCK()                                \
   if (!sys_thread_tcpip(LWIP_CORE_LOCK_QUERY_HOLDER)) { \
@@ -189,7 +193,7 @@ static bool _udp_task_start() {
   }
   if (!_udp_task_handle) {
     xTaskCreateUniversal(
-      _udp_task, "async_udp", 4096, NULL, CONFIG_ARDUINO_UDP_TASK_PRIORITY, (TaskHandle_t *)&_udp_task_handle, CONFIG_ARDUINO_UDP_RUNNING_CORE
+      _udp_task, "async_udp", CONFIG_ARDUINO_UDP_TASK_STACK_SIZE, NULL, CONFIG_ARDUINO_UDP_TASK_PRIORITY, (TaskHandle_t *)&_udp_task_handle, CONFIG_ARDUINO_UDP_RUNNING_CORE
     );
     if (!_udp_task_handle) {
       return false;