First stab at fixing MQTT topic paths for HA discovery in 2023.8+

[aarontc]

HomeAssistant 2023.8 changed the naming requirements for MQTT entities - entity names can no longer contain the device name. This means multiple entities might have the same name if you have multiple instances of the same device type, and they will clobber each other with the existing discovery topic naming scheme. This change inserts the host into the discovery topic name to avoid the clobbering.