Tweak spacing for horizontal preferences.

- Add minHeight to horizontal preference so they are not clustered
together.
- Wrap app_data_usage's into different categories so they don't rely on
SpacePreference to draw space and dividers.

Change-Id: Ieed90a39d48494d1207680483968b5733bdfb344
Fix: 37750568
Test: visual
(cherry picked from commit 9c93c28b)