Add multi-meter energy sender schema with UART0/1/2 mode split

include/meter_driver.h

@@ -1,9 +1,8 @@
 #pragma once
 
 #include <Arduino.h>
-#include "data_model.h"
 
 void meter_init();
-bool meter_read(MeterData &data);
-bool meter_poll_frame(const char *&frame, size_t &len);
-bool meter_parse_frame(const char *frame, size_t len, MeterData &data);
+void meter_poll();
+uint8_t meter_count();
+bool meter_get_last_energy_kwh(uint8_t meter_idx, uint32_t &out_energy_kwh);