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/security/ShowPasswordPreferenceController.java

@@ -44,10 +44,11 @@ public class ShowPasswordPreferenceController extends TogglePreferenceController
     }
 
     @Override
-    public void setChecked(boolean isChecked) {
+    public boolean setChecked(boolean isChecked) {
         Settings.System.putInt(mContext.getContentResolver(), Settings.System.TEXT_SHOW_PASSWORD,
                 isChecked ? 1 : 0);
         mLockPatternUtils.setVisiblePasswordEnabled(isChecked, MY_USER_ID);
+        return true;
     }
 
     @Override