New color scheme for voice assistant

[jlpouffier]

For each of the 4 voice assistant boards with LEDs as visual feedback

I created two effects

• A "Slow Pulse" for when the device is Listening
• A "Fast Pulse" for when the device is "Processing"

Note that I considered the beginning of the Processing on_stt_vad_end so that users with slow STT engine are included

I kept @kbx81 "Warm white settings" for the idle state