[material_ui] Remove widgets import in animated_icon_test.dart and autocomplete_test.dart (#12000)

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

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

## Pre-Review Checklist

Author: QuncCccccc

…_disabled_tests/animated_icons_test.dart …aterial_ui/test/animated_icons_test.dartpackages/material_ui/temporarily_disabled_tests/animated_icons_test.dart renamed to packages/material_ui/test/animated_icons_test.dart packages/material_ui/temporarily_disabled_tests/animated_icons_test.dart renamed to packages/material_ui/test/animated_icons_test.dart

@@ -2,17 +2,15 @@
 // 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.',
-)
 @Tags(<String>['reduced-test-set'])
 library;
 
 import 'dart:math' as math show pi;
 
-import 'package:material_ui/material_ui.dart';
 import 'package:flutter_test/flutter_test.dart';
-import '../widgets/semantics_tester.dart';
+import 'package:material_ui/material_ui.dart';
+
+import 'semantics_tester.dart';
 
 class MockCanvas extends Fake implements Canvas {
   late Path capturedPath;

…ly_disabled_tests/autocomplete_test.dart …/material_ui/test/autocomplete_test.dartpackages/material_ui/temporarily_disabled_tests/autocomplete_test.dart renamed to packages/material_ui/test/autocomplete_test.dart packages/material_ui/temporarily_disabled_tests/autocomplete_test.dart renamed to packages/material_ui/test/autocomplete_test.dart

@@ -2,14 +2,11 @@
 // 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:material_ui/material_ui.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:material_ui/material_ui.dart';
 
-import '../widgets/semantics_tester.dart';
+import 'semantics_tester.dart';
 
 class User {
   const User({required this.email, required this.name});