fix(mqtt_cxx): Fix clang-tidy warnings with C++ exceptions

Author: david-cermak

test_app/sdkconfig.defaults

@@ -9,6 +9,10 @@ CONFIG_PARTITION_TABLE_FILENAME="partitions.csv"
 CONFIG_HEAP_POISONING_COMPREHENSIVE=y
 CONFIG_COMPILER_STACK_CHECK_MODE_STRONG=y
 CONFIG_COMPILER_STACK_CHECK=y
+
+# since mqtt-cxx uses exceptions
+CONFIG_COMPILER_CXX_EXCEPTIONS=y
+
 CONFIG_ESP_MAIN_TASK_STACK_SIZE=16000
 CONFIG_FREERTOS_WATCHPOINT_END_OF_STACK=y