v1.8.0: Audio 代码重构与低功耗优化 (#943)

* Reconstruct Audio Code

* Remove old IoT implementation

* Add MQTT-UDP documentation

* OTA升级失败时，可以继续使用

main/protocols/mqtt_protocol.h

@@ -26,7 +26,7 @@ public:
     ~MqttProtocol();
 
     bool Start() override;
-    bool SendAudio(const AudioStreamPacket& packet) override;
+    bool SendAudio(std::unique_ptr<AudioStreamPacket> packet) override;
     bool OpenAudioChannel() override;
     void CloseAudioChannel() override;
     bool IsAudioChannelOpened() const override;