UriItem should have UriWidget as default_widget

Problem/Motivation

UriItem does not declare a default_widget so it cannot be used in an entity form unless the widget is specified explicitly.

// This should suffice and it does for other field types.
// The default widget is picked automatically.
BaseFieldDefinition::create('uri')
  ->setDisplayOptions('form', ['weight' => 0]);

// In fact, the following is needed, though.
BaseFieldDefinition::create('uri')
  ->setDisplayOptions('form', [
    'type' => 'uri',
    'weight' => 0,
]);

Proposed resolution

Because we already have a UriWidget the solution is trivial: Add a default_widget declaration to the UriItem annotation.

Specifically, find core\lib\Drupal\Core\Field\Plugin\Field\FieldType\UriItem.php and add a line of the form default_widget = "uri" to the annotation (the @FieldType stuff at the top of the file).

Remaining tasks

User interface changes

None

API changes

None

Data model changes

None

Beta phase evaluation