Update the automatic storage management preferences.

This updates this page to match the newer mocks. The changes
include:

* Changing the toggle from a switch to a switch bar.
* Removing the Deletion Helper flow from the screen.
* Unit testing the previously untested functionality.

Change-Id: I35eb1e065c9acfbf32a64d659d35e18034025472
Fixes: 36486021
Test: Robotest