Add labels to intensity slider and flip labels

Labels are Dimmer and Brighter. As the slider value is lowered,
the dimming intensity is increased

Slider min = 100 - intensity max
Slider max = 100 - intensity min

Ex: If intensity max = 80, the slider min with be 20. If the user
moves the position to the minimum end we'll send 80 to Color DisplayManager

Test: atest ReduceBrightColorsIntensityPreferenceControllerTest,
manual
Bug: 190722076

Change-Id: Ib05ba38805b8fa1f68c144a3929027899df70abf