Updates main page for Do Not Disturb

Settings > Sound > Do Not Disturb
- Update strings, more descriptive summary for DND Apps summary
- Move top-level ordering of preferences
- Remove old unused DND strings

Test: make RunSettingsRoboTests7
Test: make ROBOTEST_FILTER=ZenModeBypassingAppsPreferenceControllerTest RunSettingsRoboTests
Test: manual
Bug: 151845457
Change-Id: I9c23c558a9d764702e966d22e5c6e5c5425e4d32

res/layout/zen_mode_settings_button.xml

@@ -39,7 +39,6 @@
         android:layout_height="wrap_content"
         android:layout_gravity="left"
         android:gravity="center"
-        android:paddingTop="@dimen/zen_mode_button_padding_vertical"
         android:text="@string/zen_mode_button_turn_on"/>
 
     <Button
@@ -51,7 +50,6 @@
         android:layout_height="wrap_content"
         android:layout_gravity="left"
         android:gravity="center"
-        android:paddingTop="@dimen/zen_mode_button_padding_vertical"
         android:text="@string/zen_mode_button_turn_off" />
 
 </LinearLayout>