Follow O patterns for a11y settings

Move the summary for the toggled features to a footer.
Make the settings appear as a preference.

Bug: 36780887
Test: Start settings and observe the new UI looks a lot
like the mocks referenced in the bug. Also added unit
test to verify that summary text shows up.

Change-Id: I1d002b194991d0901ecb27198ba5de73bd23a5a9

src/com/android/settings/accessibility/ToggleScreenMagnificationPreferenceFragment.java

@@ -144,7 +144,6 @@ public class ToggleScreenMagnificationPreferenceFragment extends
         final PreferenceScreen preferenceScreen = getPreferenceManager().getPreferenceScreen();
         preferenceScreen.setOrderingAsAdded(false);
         mVideoPreference.setOrder(0);
-        mSummaryPreference.setOrder(1);
         mConfigWarningPreference.setOrder(2);
         preferenceScreen.addPreference(mVideoPreference);
         preferenceScreen.addPreference(mConfigWarningPreference);