Please add DSMR support for Sanxing SX6x1 meters (E.on - Émász Hungary)

**Describe the problem you have/What new integration you would like**
Please add DSMR support for Sanxing SX6x1 smart meters (E.on and MVM Émász/ELMŰ in Hungary).
Sends data at 115200 baud every 10 seconds.

**Please describe your use case for this integration and alternatives you've tried:**
Works with [Tasmota](https://tasmota.github.io/docs/Smart-Meter-Interface/#sanxing-sx6x1-sxxu1x-ascii-obis) - see for OBISes and example data.

**Additional context**
Official OBIS codes description (same): [E.on](https://www.eon.hu/content/dam/eon/eon-hungary/documents/Muszaki-ugyek/Fogyasztasmerok-leirasa/sanxing-sx6x1/EON-leiras-az-ugyfelek-szamara-SX6X1-S12U16-S34U18-V010.pdf) and [MVM-Émász](https://mvmemaszhalozat.hu/elmu/file/downloadfile?id=e7d5d332-ce9a-483d-9dc8-7baf0fe42ab1) (last pages on both documents).

Start with the linked Tasmota Sanxing SX6x1 documentation and example data, then compare the OBIS descriptions in the linked E.on and MVM-Émász PDFs. Done means DSMR support handles the meter's 115200-baud output, including the documented OBIS values and its 10-second transmission interval.

Written by the indexing model from the issue text.