Rename night color to night light

Night Light goes under three names currently:

• ColorCorrect
• NightColor
• NightLight

it's messy, it would be great to clean things up a bit.

Changing the class names shouldn't be a problem. Changing the d-bus interface can be considered as an api breaking change and it is preferred to avoid such changes in minor releases if possible.

The types can be renamed later, but the d-bus interfaces may need to be renamed in 6.0 to avoid breaking API in 6.1.