Add a widget with hidden geofield textarea to receive autocomplete geocode values.

We already have the alteration on the leaflet widget that works much the same. Leaflet widget allows you to toggle the visibility of this textarea field. We also have a latlon alteration so Geofields Lat/Lon widget can be autopopulated. It is however displayed, unless the person implementing the site hides it with an _alter. The Geofield text area, without leaflet map, also displays. Adding an config option to hide it isn't considered for upstream. This produces one that is hidden, gets our javascript attached directly, and hence can be described as such too.

Closes #3538723