Dynamic update a11y settings when a11y service target is disabled

Root cause: A11y settings only handle the package install/uninstall/update, but it does not observe the component status.
Solution: Add onPackageModified() to refresh the list.

Bug: 264697450
Test: Manual test
Change-Id: I779c4ba87c6f54616e9c4c6378db91d9ff611b24

src/com/android/settings/accessibility/AccessibilitySettings.java

@@ -31,6 +31,7 @@ import android.text.TextUtils;
 import android.util.ArrayMap;
 import android.view.accessibility.AccessibilityManager;
 
+import androidx.annotation.NonNull;
 import androidx.annotation.VisibleForTesting;
 import androidx.preference.Preference;
 import androidx.preference.PreferenceCategory;
@@ -113,6 +114,11 @@ public class AccessibilitySettings extends DashboardFragment {
             sendUpdate();
         }
 
+        @Override
+        public void onPackageModified(@NonNull String packageName) {
+            sendUpdate();
+        }
+
         @Override
         public void onPackageAppeared(String packageName, int reason) {
             sendUpdate();