[material_ui] Remove widgets/clipboard_utils.dart imports from date_picker_test.dart, input_date_picker_form_field_test.dart, search_test.dart, selectable_text_test.dart, text_form_field_test.dart, text_selection_test.dart (#12030)

~**Test failures are expected. This PR should land after #12022

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

This PR:
* Removed the cross-import of `widgets/clipboard_utils.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.

This PR is to port over the changes in flutter/flutter#184278

## Pre-Review Checklist

Author: QuncCccccc

…ily_disabled_tests/date_picker_test.dart …s/material_ui/test/date_picker_test.dartpackages/material_ui/temporarily_disabled_tests/date_picker_test.dart renamed to packages/material_ui/test/date_picker_test.dart packages/material_ui/temporarily_disabled_tests/date_picker_test.dart renamed to packages/material_ui/test/date_picker_test.dart

@@ -2,21 +2,20 @@
 // 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.',
-)
 // This file is run as part of a reduced test set in CI on Mac and Windows
 // machines.
 @Tags(<String>['reduced-test-set'])
 library;
 
+import 'dart:async';
 import 'dart:ui';
 
-import 'package:material_ui/material_ui.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
-import '../widgets/clipboard_utils.dart';
+import 'package:material_ui/material_ui.dart';
+
+import 'clipboard_utils.dart';
 
 void main() {
   TestWidgetsFlutterBinding.ensureInitialized();
@@ -2191,12 +2190,14 @@ void main() {
       );
 
       final BuildContext context = tester.element(find.text('Test'));
-      showDatePicker(
-        context: context,
-        initialDate: DateTime.now(),
-        firstDate: DateTime(2018),
-        lastDate: DateTime(2030),
-        anchorPoint: const Offset(1000, 0),
+      unawaited(
+        showDatePicker(
+          context: context,
+          initialDate: DateTime.now(),
+          firstDate: DateTime(2018),
+          lastDate: DateTime(2030),
+          anchorPoint: const Offset(1000, 0),
+        ),
       );
       await tester.pumpAndSettle();
 
@@ -2229,11 +2230,13 @@ void main() {
       );
 
       final BuildContext context = tester.element(find.text('Test'));
-      showDatePicker(
-        context: context,
-        initialDate: DateTime.now(),
-        firstDate: DateTime(2018),
-        lastDate: DateTime(2030),
+      unawaited(
+        showDatePicker(
+          context: context,
+          initialDate: DateTime.now(),
+          firstDate: DateTime(2018),
+          lastDate: DateTime(2030),
+        ),
       );
       await tester.pumpAndSettle();
 
@@ -2266,11 +2269,13 @@ void main() {
       );
 
       final BuildContext context = tester.element(find.text('Test'));
-      showDatePicker(
-        context: context,
-        initialDate: DateTime.now(),
-        firstDate: DateTime(2018),
-        lastDate: DateTime(2030),
+      unawaited(
+        showDatePicker(
+          context: context,
+          initialDate: DateTime.now(),
+          firstDate: DateTime(2018),
+          lastDate: DateTime(2030),
+        ),
       );
       await tester.pumpAndSettle();
 

…s/input_date_picker_form_field_test.dart …t/input_date_picker_form_field_test.dartpackages/material_ui/temporarily_disabled_tests/input_date_picker_form_field_test.dart renamed to packages/material_ui/test/input_date_picker_form_field_test.dart packages/material_ui/temporarily_disabled_tests/input_date_picker_form_field_test.dart renamed to packages/material_ui/test/input_date_picker_form_field_test.dart

@@ -2,16 +2,13 @@
 // 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:flutter/foundation.dart';
-import 'package:material_ui/material_ui.dart';
 import 'package:flutter/semantics.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:material_ui/material_ui.dart';
 
-import '../widgets/clipboard_utils.dart';
+import 'clipboard_utils.dart';
 
 class TestMaterialLocalizations extends DefaultMaterialLocalizations {
   @override

…porarily_disabled_tests/search_test.dart …ckages/material_ui/test/search_test.dartpackages/material_ui/temporarily_disabled_tests/search_test.dart renamed to packages/material_ui/test/search_test.dart packages/material_ui/temporarily_disabled_tests/search_test.dart renamed to packages/material_ui/test/search_test.dart

@@ -2,18 +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.',
-)
 import 'dart:ui';
 
 import 'package:flutter/foundation.dart';
-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/clipboard_utils.dart';
-import '../widgets/semantics_tester.dart';
+import 'clipboard_utils.dart';
+import 'semantics_tester.dart';
 
 void main() {
   TestWidgetsFlutterBinding.ensureInitialized();

…disabled_tests/selectable_text_test.dart …terial_ui/test/selectable_text_test.dartpackages/material_ui/temporarily_disabled_tests/selectable_text_test.dart renamed to packages/material_ui/test/selectable_text_test.dart packages/material_ui/temporarily_disabled_tests/selectable_text_test.dart renamed to packages/material_ui/test/selectable_text_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.',
-)
 // This file is run as part of a reduced test set in CI on Mac and Windows
 // machines.
 @Tags(<String>['reduced-test-set'])
@@ -17,15 +14,15 @@ import 'dart:ui';
 import 'package:cupertino_ui/cupertino_ui.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
-import 'package:material_ui/material_ui.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:leak_tracker_flutter_testing/leak_tracker_flutter_testing.dart';
+import 'package:material_ui/material_ui.dart';
 
-import '../widgets/clipboard_utils.dart';
-import '../widgets/semantics_tester.dart';
+import 'clipboard_utils.dart';
 import 'editable_text_utils.dart' show textOffsetToPosition;
+import 'semantics_tester.dart';
 
 class MaterialLocalizationsDelegate extends LocalizationsDelegate<MaterialLocalizations> {
   @override

…disabled_tests/text_form_field_test.dart …terial_ui/test/text_form_field_test.dartpackages/material_ui/temporarily_disabled_tests/text_form_field_test.dart renamed to packages/material_ui/test/text_form_field_test.dart packages/material_ui/temporarily_disabled_tests/text_form_field_test.dart renamed to packages/material_ui/test/text_form_field_test.dart

@@ -2,20 +2,17 @@
 // 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 'dart:ui';
 
 import 'package:cupertino_ui/cupertino_ui.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
-import 'package:material_ui/material_ui.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:material_ui/material_ui.dart';
 
-import '../widgets/clipboard_utils.dart';
+import 'clipboard_utils.dart';
 import 'editable_text_utils.dart';
 
 void main() {

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

@@ -2,20 +2,17 @@
 // 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.',
-)
 // This file is run as part of a reduced test set in CI on Mac and Windows
 // machines.
 @Tags(<String>['reduced-test-set'])
 library;
 
-import 'package:material_ui/material_ui.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:material_ui/material_ui.dart';
 
-import '../widgets/clipboard_utils.dart';
+import 'clipboard_utils.dart';
 import 'editable_text_utils.dart' show findRenderEditable, globalize, textOffsetToPosition;
 
 void main() {