Refactor the layout for MasterSwitch to a 2 target pref

And move the layout to settingslib.

The new TwoTargetPreference is a preference object that has a vertical
divider between main panel and widget (if it exists).

Converted master switch, restricted preference, gear preference to use
the new style

Change-Id: Ia3848cebb06b8edc4e60abf9b0caf13cdb29c22c
Fix: 36511169
Test: make RunSettingsRoboTests