Add connection state (online/offline) to every z2m device (or other MQTT device)

Hi Roma,

The first error should be resolved after you have force removed the config_entries and entity_registry.
I did extensive adding and removing tests, and I did not encouter this error.

Please send the whole debug log, so I can debug what happend that caused this error.
It would be even better if you can find the log from before the remove, than I can debug what was causing the block in the startup fase.

Kind regards,
- Ingrid