[audio_adc] Add new `audio_adc` component (#8094)

esphome/components/audio_adc/audio_adc.h

@@ -0,0 +1,17 @@
+#pragma once
+
+#include "esphome/core/defines.h"
+#include "esphome/core/hal.h"
+
+namespace esphome {
+namespace audio_adc {
+
+class AudioAdc {
+ public:
+  virtual bool set_mic_gain(float mic_gain) = 0;
+
+  virtual float mic_gain() = 0;
+};
+
+}  // namespace audio_adc
+}  // namespace esphome