Input: Evaluate to prevent an additional "state" icon tag

[mfranzke]

    Let's try to avoid this tag and use the existing wrapping one within another evaluation.

Originally posted by @mfranzke in db-ui/core#198 (comment)

[mfranzke]

obsolete, as we'll still provide the possibility to set an before and after icon, but would additionally need a state icon, which we couldn't handle depending on only two available slots (:before and :after).