[cupertino_ui] Migrate button_test.dart to SemanticsHandle (#11992)

Part of flutter/flutter#182636 and flutter/flutter#188395

This PR:
* Removed the cross-import of `widgets/semantics_tester.dart`. Replaced `SemanticsTester` with `SemanticsHandle`.
* Removed `@Skip` annotation, all tests in this file has passed. `semantics_tester.dart` has existed in `cupertino_ui`, so we can directly import `semantics_tester.dart`;
* Moved the file to `test/` folder.

## Pre-Review Checklist

Author: Renzo-Olivares

…porarily_disabled_tests/button_test.dart …kages/cupertino_ui/test/button_test.dartpackages/cupertino_ui/temporarily_disabled_tests/button_test.dart renamed to packages/cupertino_ui/test/button_test.dart packages/cupertino_ui/temporarily_disabled_tests/button_test.dart renamed to packages/cupertino_ui/test/button_test.dart

@@ -2,9 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-@Skip(
-  'This file is skipped due to a cross-import that needs to be fixed. Tracked in https://github.com/flutter/flutter/issues/177028.',
-)
 import 'package:cupertino_ui/cupertino_ui.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
@@ -13,8 +10,6 @@ import 'package:flutter/scheduler.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 
-import '../widgets/semantics_tester.dart';
-
 const TextStyle testStyle = TextStyle(fontSize: 10.0, letterSpacing: 0.0);
 
 void main() {
@@ -348,7 +343,8 @@ void main() {
   });
 
   testWidgets('Cupertino button is semantically a button', (WidgetTester tester) async {
-    final semantics = SemanticsTester(tester);
+    final SemanticsHandle handle = tester.ensureSemantics();
+
     await tester.pumpWidget(
       boilerplate(
         child: Center(
@@ -358,24 +354,17 @@ void main() {
     );
 
     expect(
-      semantics,
-      hasSemantics(
-        TestSemantics.root(
-          children: <TestSemantics>[
-            TestSemantics.rootChild(
-              actions: SemanticsAction.tap.index | SemanticsAction.focus.index,
-              label: 'ABC',
-              flags: <SemanticsFlag>[SemanticsFlag.isButton, SemanticsFlag.isFocusable],
-            ),
-          ],
-        ),
-        ignoreId: true,
-        ignoreRect: true,
-        ignoreTransform: true,
+      tester.getSemantics(find.text('ABC')),
+      isSemantics(
+        label: 'ABC',
+        isButton: true,
+        isFocusable: true,
+        hasTapAction: true,
+        hasFocusAction: true,
       ),
     );
 
-    semantics.dispose();
+    handle.dispose();
   });
 
   testWidgets('Can specify colors', (WidgetTester tester) async {