[SolaxX1] Add meter mode

[SteWers]

Description:

Introduce the 'MeterMode' regarding to the implementation from @syssi. The driver automatically detects when the inverter requests the meter mode. Only one mode is possilbe at the same time.

The meter values can be communicated to the driver via this commands:

• EnergyConfig MeterPower current imported or exported power in W
• EnergyConfig MeterImport imported energy in kWh to be displayed on the inverter
• EnergyConfig MeterExport exported energy in kWh to be displayed on the inverter

A good way for operation is to subscribe to the smart meter MQTT topics directly. Therefore compile with #define SUPPORT_MQTT_EVENT.

A sample rule can look like this:

Rule1
ON mqtt#connected DO Subscribe PwrEvt, MT175/tele/SENSOR ENDON
ON Event#PwrEvt#SML#Power_all DO EnergyConfig MeterPower %value% ENDON
ON Event#PwrEvt#SML#Total_in DO EnergyConfig MeterImport %value% ENDON
ON Event#PwrEvt#SML#Total_out DO EnergyConfig MeterExport %value% ENDON

Checklist:

• The pull request is done against the latest development branch
• Only relevant files were touched
• Only one feature/fix was added per PR and the code change compiles without warnings
• The code change is tested and works with Tasmota core ESP8266 V.2.7.8
• The code change is tested and works with Tasmota core ESP32 V.3.1.0.241015
• I accept the CLA.

[syssi]

Good job!