Convert EncryptionAndCredential into DashboardFragment

The logic still lives in fragment for now. They will be moved into
PrefControllers in follow-up changes.

Bug: 32953042
Test: RoboTests
Change-Id: I2b03d26b5f4e6bbb37b42f9dc83a9464eb169868

src/com/android/settings/dashboard/DashboardFragment.java

@@ -183,6 +183,9 @@ public abstract class DashboardFragment extends SettingsPreferenceFragment
         }
     }
 
+    @Override
+    protected abstract int getPreferenceScreenResId();
+
     protected <T extends AbstractPreferenceController> T getPreferenceController(Class<T> clazz) {
         AbstractPreferenceController controller = mPreferenceControllers.get(clazz);
         return (T) controller;