Support Kamstrup Omnipower energy meter

**Describe the problem you have/What new integration you would like**

Add support for the [Kamstrup omnipower energy meter](https://www.kamstrup.com/da-dk/elloesninger/intelligente-elmaalere/3-faset-elmaaler) that is used in parts of denmark.

**Please describe your use case for this integration and alternatives you've tried:**

An easier way for people to get data from the energy meter.

**Additional context**

This repo https://github.com/Claustn/esp8266-kamstrup-mqtt already contains a simple implementation that can be deployed on an esp.

The user will need to supply 2 keys that they need to get from the energy company.

Start by reviewing the linked Claustn/esp8266-kamstrup-mqtt implementation and the Kamstrup Omnipower documentation to understand the meter protocol and the two required keys. Then locate the project’s existing integration entry points and credential handling. Done means users can configure both keys and retrieve data from the meter, but the issue does not identify files or tests.

Written by the indexing model from the issue text.