Add Tapjacking Protection for SettingsHomepageActivity

Add/remove the SYSTEM_FLAG_HIDE_NON_SYSTEM_OVERLAY_WINDOWS flag into/from
SettingsHomepageActivity and SettingsPanelActivity with lifecycle.

Bug: 138442483
Test: make RunSettingsRoboTests ROBOTEST_FILTER=com.android.settings.homepage
      make RunSettingsRoboTests ROBOTEST_FILTER=com.android.settings.panel
      manual test
Change-Id: I72f9a947f57f74a8c09127d6c39173594c248ddc

src/com/android/settings/panel/SettingsPanelActivity.java

@@ -32,6 +32,7 @@ import androidx.fragment.app.FragmentManager;
 
 import com.android.internal.annotations.VisibleForTesting;
 import com.android.settings.R;
+import com.android.settings.core.HideNonSystemOverlayMixin;
 
 /**
  * Dialog Activity to host Settings Slices.
@@ -62,6 +63,7 @@ public class SettingsPanelActivity extends FragmentActivity {
     protected void onCreate(@Nullable Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         createOrUpdatePanel(true /* shouldForceCreation */);
+        getLifecycle().addObserver(new HideNonSystemOverlayMixin(this));
     }
 
     @Override