Re-style stopwatch notification to match that of timer.

Bug: 23936610

Restyling for L+; KK is unaffected.
Fixed font style/caps/color.
Fixed left-alignment.
Switched order of actions so start/stop is on the left (like timer).
Removed vertical divider bar.
Added padding to horizontal divider.
Tinted action icons to proper gray.

Change-Id: I48131fd30738aad692a70a7adb1a3e5c583483e8