Hidden elements doesn't need an extra element in the DOM, but OOUIHTMLForm
would render one, wrapped into a fieldLayout div.
Fix this by adding the possibility to bypass the output, and only construct
a HTMLFormField element and run the output method.
Bug: T117768
Change-Id: I8c9d2ff862f1b14d72a9bb9e1a51e8745af6d1f4