Add more Arduino/FreeRTOS test stubs so that eModbus builds in ESP32 mode.

test/emul/freertos/FreeRTOS.cpp

@@ -0,0 +1,10 @@
+#include "FreeRTOS.h"
+
+extern "C" {
+BaseType_t xTaskCreatePinnedToCore(TaskFunction_t pxTaskCode, const char* const pcName, const uint32_t ulStackDepth,
+                                   void* const pvParameters, UBaseType_t uxPriority, TaskHandle_t* const pxCreatedTask,
+                                   const BaseType_t xCoreID) {
+  return 0;
+}
+void vTaskDelete(TaskHandle_t xTaskToDelete) {}
+}