Update docs on ChangeNotifier.dispose and KeepAliveHandle.release (#108384)

packages/flutter/lib/src/foundation/change_notifier.dart

@@ -297,6 +297,10 @@ class ChangeNotifier implements Listenable {
   /// [addListener] will throw after the object is disposed).
   ///
   /// This method should only be called by the object's owner.
+  ///
+  /// This method does not notify listeners, and clears the listener list once
+  /// it is called. Consumers of this class must decide on whether to notify
+  /// listeners or not immediately before disposal.
   @mustCallSuper
   void dispose() {
     assert(ChangeNotifier.debugAssertNotDisposed(this));

packages/flutter/lib/src/widgets/automatic_keep_alive.dart

@@ -321,9 +321,22 @@ class KeepAliveNotification extends Notification {
 class KeepAliveHandle extends ChangeNotifier {
   /// Trigger the listeners to indicate that the widget
   /// no longer needs to be kept alive.
+  ///
+  /// This method does not call [dispose]. When the handle is not needed
+  /// anymore, it must be [dispose]d regardless of whether notifying listeners.
+  @Deprecated(
+    'Use dispose instead. '
+    'This feature was deprecated after v3.3.0-0.0.pre.',
+  )
   void release() {
     notifyListeners();
   }
+
+  @override
+  void dispose() {
+    notifyListeners();
+    super.dispose();
+  }
 }
 
 /// A mixin with convenience methods for clients of [AutomaticKeepAlive]. Used
@@ -354,7 +367,6 @@ mixin AutomaticKeepAliveClientMixin<T extends StatefulWidget> on State<T> {
 
   void _releaseKeepAlive() {
     // Dispose and release do not imply each other.
-    _keepAliveHandle!.release();
     _keepAliveHandle!.dispose();
     _keepAliveHandle = null;
   }