add prometheus metrics for analog/scheduler/custom #2962

src/core/analogsensor.h

@@ -177,6 +177,7 @@ class AnalogSensor {
     bool                        update(uint8_t gpio, const char * name, double offset, double factor, uint8_t uom, int8_t type, bool deleted, bool is_system);
     bool                        get_value_info(JsonObject output, const char * cmd, const int8_t id = -1);
     void                        store_counters();
+    std::string                 get_metrics_prometheus();
     static std::vector<uint8_t> exclude_types() {
         return exclude_types_;
     }