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/boards/common/sleep_timer.h

@@ -0,0 +1,32 @@
+#pragma once
+
+#include <functional>
+
+#include <esp_timer.h>
+#include <esp_pm.h>
+
+class SleepTimer {
+public:
+    SleepTimer(int seconds_to_light_sleep = 20, int seconds_to_deep_sleep = -1);
+    ~SleepTimer();
+
+    void SetEnabled(bool enabled);
+    void OnEnterLightSleepMode(std::function<void()> callback);
+    void OnExitLightSleepMode(std::function<void()> callback);
+    void OnEnterDeepSleepMode(std::function<void()> callback);
+    void WakeUp();
+
+private:
+    void CheckTimer();
+
+    esp_timer_handle_t sleep_timer_ = nullptr;
+    bool enabled_ = false;
+    int ticks_ = 0;
+    int seconds_to_light_sleep_;
+    int seconds_to_deep_sleep_;
+    bool in_light_sleep_mode_ = false;
+
+    std::function<void()> on_enter_light_sleep_mode_;
+    std::function<void()> on_exit_light_sleep_mode_;
+    std::function<void()> on_enter_deep_sleep_mode_;
+};