SystemUI: visualizer tile improvements

  - Decrease width to match other icons better
  - Don't hide the tile when there's no music playing, instead, just
    show the static image, and don't hide the icon
  - Line up static image and visualizer iamge
  - Move visualizer color overlay to cm_colors for theming discoverability

Change-Id: I22fa55d3f95602b8ad6f486ef83378cde610fe1d
Signed-off-by: Roman Birg <roman@cyngn.com>