Adjust notification dots

- Use consistent bounds for folders as other icons, to ensure dot
  has a consistent placement (moved right+up a bit)
- Strengthen the ambient shadow to improve contrast
  - Increased blur size and opacity
- Use a dark gray rather than black for dots on dark folders

Bug: 73331123
Change-Id: I888f4645d3a48465af93f5003dda8f8b7c3129f3