Avoid scaffolding the default view layout for default Folderish doctypes

When scaffolding a layout for a default document type, we use the default layout definition that comes from the Web UI, as is, if that layout exists. The problem is that for the majority of the default document types with the Folderish facet, that means that the default "view" layout contains only a single element: <nuxeo-document-content>.

If the goal of the user is to perform any sort of customization (changing the column order, for example), this far from ideal. This element was created to encapsulate all the logic dedicated to show the children of a folderish document and was never meant to be parameterizable.

The goal is to treat this case like a layout for a custom folderish document type, and instead of providing the default layout for the document type, scaffold an entirely new one based on the folderish view template.

Note: The drawback of this approach is that if at some point the default layouts are updated to include additional functionality, we won't be able to take advantage of that. Unfortunately, this appears to be the best solution.
(Maybe in the future we allow users to choose between generating the layout from the default one, or scaffold a new one entirely)