Link widget doesn't support Link fields without a title

[pfaocle]

Ref: https://github.com/ixis/codeception-drupal-content-types/blob/master/src/Drupal/ContentTypeRegistry/Widgets/LinkWidget.php

Link fields as currently implemented require both a URL and a title. This is not always the case as some fields may be configured to have the title optional or not available at all.

The Link widget should ideally support Link fields configured to use optional, required, static or no titles.