Provide link field with no input validation

Our current link field as we have it defined is for internal links (refer to docu https://docs.magnolia-cms.com/product-docs/Templating/Dialog-definition/Field-definition/List-of-fields/Link-field.html // “The link field is used to select targets inside Magnolia” // same for the M5 UI).

As such it makes sense that we do not allow paths that have no matching target and that is an improvement compared to the previous version.

We have customers who have used this field for external addresses too though. In the M5 UI that was possible due to the lack of validation.

Bringing back a textfield-like link field may be a short-term solution before we have MGNLUI-6566 in place.