[feat] - Proxy "Dumb" Climate entity

[jack3308]

Add the option for the user to provide a climate entity already exposed in home assistant that dual-smart-thermostat should control instead of providing heating and/or cooling switches. This would be useful for bridging the gap left by so many crappy OEM integrations that don't provide pretty key components for a climate entity. Examples would be the Panasonic Comfort Cloud devices don't have temperature sensors exposed and so you don't have any idea what temperature the room is or if it's even heating or cooling to the set temperature. Additionally, this allows for easy addition of things like entry sensors, presets, and the like that have been half forgot by crappy OEM integrations.