Replace 'SirenActionFieldType' with 'HtmlInputType'

[ingogriebsch]

Spring HATEOAS introduced HtmlInputType. Spring HATEOAS Siren currently implements the same idea through SirenActionFieldType. It is probably not necessary to implement it on our own if the underyling basis provides the same feature. Therefore we should replace the one with the other. But we also don't want to introduce a breaking change with a minor or patch update, means we will solve this ticket with a major version update.