esp_modem: Add missing AT commands to plain C-API

components/esp_modem/include/cxx_include/esp_modem_dce_module.hpp

@@ -79,6 +79,7 @@ public:
             }
             return true;
         } else if (mode == modem_mode::COMMAND_MODE) {
+            Task::Delay(1000); // Mandatory 1s pause
             return set_command_mode() == command_result::OK;
         } else if (mode == modem_mode::CMUX_MODE) {
             return set_cmux() == command_result::OK;

components/esp_modem/include/cxx_include/esp_modem_primitives.hpp

@@ -76,6 +76,7 @@ public:
 
     static void Delete();
     static void Relinquish();
+    static void Delay(uint32_t delay);
 private:
     TaskT task_handle;
 };