Move creation of $widget into WidgetBrowserTestBase

Unpostponing now that #3109923: Deprecation: add $defaultTheme - create FormWidgetBrowserTestBase class is done

and I forgot the vital change

Checking back with the problems we found on #3109923: Deprecation: add $defaultTheme - create FormWidgetBrowserTestBase class, in summary

1. If our WidgetBrowserTestBase has protected function setUp($widgetId): void { we get the error that it does not match with BrowserTestBase: Declaration of Drupal\Tests\typed_data\Functional\TypedDataFormWidget\FormWidgetBrowserTestBase::setUp($widgetId) should be compatible with Drupal\Tests\BrowserTestBase::setUp() which means we have to have a default value for $widgetId
2. Therefore we need it be protected function setUp($widgetId = ''): void {, which causes the error that the individual test's setup() do not match our WidgetBrowserTestBase: Declaration of Drupal\Tests\typed_data\Functional\TypedDataFormWidget\DatetimeWidgetTest::setUp(): void should be compatible with Drupal\Tests\typed_data\Functional\TypedDataFormWidget\FormWidgetBrowserTestBase::setUp($widgetId = ''): void
3. One solution to this is for the separate test classes to have
   

   protected function setUp($widgetId = 'datetime'): void {
       parent::setUp($widgetId);
     }
   

   This actually runs fine, but we get a coding standard failure for each one, stating:

   Possible useless method overriding detected (Generic.CodeAnalysis.UselessOverridingMethod.Found)
   

4. Therefore I propose that instead of trying to create the widget directly in the base class setUp() we simply have a new function defined in the base class protected function createWidget($widgetId): void { and this can be called from the setUp() of each test class. This runs fine, has no coding standards faults and keeps the definition of the $widgetID and $widget properties and the creation of the widget all within the base class.

I moved the createUser and login into this function too, just for convenience, as we do not now have a setUp() in FormWidgetBrowserTestBase. But if you would prefer, I can create that setUp and move the single line login into it.

Needs Review. When this is done I can work on
#3109906: Textarea example form is limited to 8 character input
#3110036: Create assertIsApplicable() and assertIsNotApplicable() in widget base class
#3169256: Add test for DateTimeRange widget

Just a question, if we are working on this together then we need to agree how. I created a MR but you have provided a patch without interdiff. If you want to work with patches that ok, I just need to know.

Your changes look good. For the record, I have uploaded that interdiff. Yes that widgetId property is not needed. It was a remnant from my previous work on the preceding issue #3109923: Deprecation: add $defaultTheme - create FormWidgetBrowserTestBase class. Also moving the createUser() into a new base setUp() is much better than having it in the createWidget(). I had wondered about doing that myself.

I spotted one unnecessary 'drupalLogin(...createUser()' which I will remove in the next patch.

Patch to remove the unnecessary login & createUser. When this passes I am happy for this to be RTBC if you are.

The message above was automatically duplicated from the MR.
Thanks for the commit. I have unpostponed #3110036: Create assertIsApplicable() and assertIsNotApplicable() in widget base class