Cleanup when using "internal" flag

[gec75]

@wills106
I saw you have already used the "internal" flag 👍
But there is room for more cleanup :) ... you don't need any HA specific attributes anymore; just keep "key" and Modbus specific, but you don't need name, icon, native_unit_of_measurement, etc...

[wills106]

I think I removed all of the icons for Internal within the SolaX plugin. But I didn't have time yesterday to check if any other values are required or not. I'll have a proper look at the Solinteg plugin.

Would be good to see if there is a way to automatically purge dead entities preventing #878

[gec75]

I just had a quick look, and there are some "name", "native...", "device_class", "entity_category", etc.
There is no rush, I just wanted to mention.