Media Library Iteration

This MR proposes a few minor iterations on the media library user interface. Additionally, it solves #1248 (closed).

• ColorPalette: user a lighter gray for detail text color
• MediaCollectionViewCell: use a lighter font for descriptive text

• MediaGridCollectionCell: use a lighter font for descriptive text

• MediaCollectionViewCell: re-arrange text labels
  • This moves the NEW indicator to the right, removes the last remaining stack view and fixes the location of title description regardless of the NEW status.

• TabBar: add shadow to separate itself from media library content

Finally, a noticeable background color is set for media groups in the video screen even for the true black mode to avoid the thumbnail group looking smaller than the surrounding full size thumbnails. Additionally, this removes unnecessary transparency to improve render speed.