Merge sub pages for lock/unlock into 1 xml.

And create PreferenceControllers for each setting

The page is still pretty janky and controllers are invoked manually.
Next CL will clean these up.

Bug: 32953042
Test: TODO
Change-Id: I1d7478324f5de4fdb464d79f89086f7e79c0ee67

src/com/android/settings/bluetooth/BluetoothSwitchPreferenceController.java

@@ -98,10 +98,11 @@ public class BluetoothSwitchPreferenceController extends TogglePreferenceControl
     }
 
     @Override
-    public void setChecked(boolean isChecked) {
+    public boolean setChecked(boolean isChecked) {
         if (mBluetoothAdapter != null) {
             mBluetoothAdapter.setBluetoothEnabled(isChecked);
         }
+        return true;
     }
 
     /**