Emetering refactoring

[rpv-tomsk]

1. Added SaveState and PublishHASSDevices driver callbacks

   This allows implement other [metering] drivers which will use these callbacks.

---

2. Allow drivers to have different set of EnergySensors.

   Multiple drivers might implement different set of EnergySensors, and we need a way to publish it into HASS. Instead of DRV_GetEnergySensorNames() use in hass_init_energy_sensor_device_info(), we could pass sensor structure directly. Function DRV_GetEnergySensorNames() removed completely.

---

3. Reimplement DRV_GetReading()

   Multiple drivers might be used to get same Reading. We need a way to get value from currently used active driver. Solution: Driver should keep its 'readings' values in global array.

   Enum reading_e and appropriate global array are introduced for DRV_GetReading().

   Enum energySensor_e is local for drv_bl_shared-based drivers. Please don't get confused. :)

   Enum energySensor_e (local to drivers) might be subset of reading_e, and also could contain sensors, not available as Readings. Other Drivers could be designed completely without energySensor_e-like enums.

---

I implemented 3phase power meter hass integration using BL602, and want to publish all related code changes and my proposals. This is patch series, which I prepared for publishing from "dirty hacks I already done".

My 3phase power meter module code is dirty and build with BL602 specific. For those interested, I published that code in my repo (https://github.com/openshwprojects/OpenBK7231T_App/commit/3842a4458a4433d75462ed255a126b841fddce57).

Kindly ask maintainers to comment changes in overall. Thanks.