[mqtt.espmilighthub] Use system channel types for color temp and brightness (#13801)

[mqtt.espmilighthub] Use system channel types for color temp and brightness (#13801)

* [mqtt.espmilighthub] use system channel types for color temp and brightness

closes #10096

also add absolute color temp channel. and remove level channel when we
already have a color channel (you can link a DimmerItem to a color
channel if your light doesn't happen to have color or you want direct
control of brightness only for some reason)

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Signed-off-by: Cody Cutrer <cody@cutrer.us>