The outliner already uses the alternating row theme color as an
overlay for every other row. This uses the same color for the file
browser, instead of a hardcoded shading.
The file browser background color is slightly tweaked to match the
outliner, and the Blender Light theme is updated to use a lighter
background color like the outliner.
Reviewed by: Hans Goudey, Julian Eisel
Differential Revision: https://developer.blender.org/D8717
479ce00809