Use setBrightness() as a dimmer/fader

[CoreProduction]

The original examples faded the LEDs by updating the pixel value. What if the pixels are set to maximum, and we want to fade using the brightness function?
See the original thread

For example, this would be useful for fading a desired colour.

[CoreProduction]

This feature already works as intended.
setBrightness() was already used during firmware testing for simple dimming.