Fix some leaks and add test to test cover remaining in a simple way. (#131373)

Contributes to https://github.com/flutter/flutter/issues/130467

Filed issue: https://github.com/flutter/flutter/issues/132620

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

@@ -81,6 +81,7 @@ class ContextMenuController {
   ///  * [remove], which removes only the current instance.
   static void removeAny() {
     _menuOverlayEntry?.remove();
+    _menuOverlayEntry?.dispose();
     _menuOverlayEntry = null;
     if (_shownInstance != null) {
       _shownInstance!.onRemove?.call();

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

@@ -1371,7 +1371,9 @@ class SelectionOverlay {
   void hideHandles() {
     if (_handles != null) {
       _handles![0].remove();
+      _handles![0].dispose();
       _handles![1].remove();
+      _handles![1].dispose();
       _handles = null;
     }
   }
@@ -1480,7 +1482,9 @@ class SelectionOverlay {
     _magnifierController.hide();
     if (_handles != null) {
       _handles![0].remove();
+      _handles![0].dispose();
       _handles![1].remove();
+      _handles![1].dispose();
       _handles = null;
     }
     if (_toolbar != null || _contextMenuController.isShown || _spellCheckToolbarController.isShown) {
@@ -1500,6 +1504,7 @@ class SelectionOverlay {
       return;
     }
     _toolbar?.remove();
+    _toolbar?.dispose();
     _toolbar = null;
   }
 
@@ -1508,6 +1513,7 @@ class SelectionOverlay {
   /// {@endtemplate}
   void dispose() {
     hide();
+    _magnifierInfo.dispose();
   }
 
   Widget _buildStartHandle(BuildContext context) {

packages/flutter/test/material/text_form_field_test.dart

@@ -251,6 +251,40 @@ void main() {
     leakTrackingTestConfig: const LeakTrackingTestConfig(allowAllNotDisposed: true, allowAllNotGCed: true),
   );
 
+  testWidgetsWithLeakTracking(
+    '$SelectionOverlay is not leaking',
+    (WidgetTester tester) async {
+    final TextEditingController controller = TextEditingController(
+      text: 'blah1 blah2',
+    );
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Material(
+          child: Center(
+            child: TextField(
+              controller: controller,
+            ),
+          ),
+        ),
+      ),
+    );
+
+    final Offset startBlah1 = textOffsetToPosition(tester, 0);
+    await tester.tapAt(startBlah1);
+    await tester.pump(const Duration(milliseconds: 100));
+    await tester.tapAt(startBlah1);
+    await tester.pumpAndSettle();
+    await tester.pump();
+    controller.dispose();
+  },
+    skip: kIsWeb, // [intended] we don't supply the cut/copy/paste buttons on the web.
+    // TODO(polina-c): remove after fixing
+    // https://github.com/flutter/flutter/issues/132620
+    leakTrackingTestConfig:  const LeakTrackingTestConfig(
+      notDisposedAllowList: <String, int?>{'_InputBorderGap' : 1},
+    ),
+  );
+
   testWidgets('the desktop cut/copy/paste buttons are disabled for read-only obscured form fields', (WidgetTester tester) async {
     final TextEditingController controller = TextEditingController(
       text: 'blah1 blah2',