Merge branch '3483321-add-declarestricttypes1-to' into '2.1.x'

Issue #3483321 by tr: Add declare(strict_types=1) to all test modules

See merge request !37

tests/modules/typed_data_global_context_test/src/ContextProvider/SimpleTestContext.php

 <?php
 
+declare(strict_types=1);
+
 namespace Drupal\typed_data_global_context_test\ContextProvider;
 
 use Drupal\Core\Plugin\Context\Context;

tests/modules/typed_data_widget_test/src/FormWidgetExampleController.php

 <?php
 
+declare(strict_types=1);
+
 namespace Drupal\typed_data_widget_test;
 
 use Drupal\Core\Controller\ControllerBase;

tests/modules/typed_data_widget_test/src/FormWidgetExampleForm.php

 <?php
 
+declare(strict_types=1);
+
 namespace Drupal\typed_data_widget_test;
 
 use Drupal\Core\Form\FormBase;