Fix layout errors when using same schema and page provider ids

Application Definition:

• Nuxeo Server Version: Nuxeo Platform LTS 2019
• Packages to Install: Nuxeo Web UI

In Modeler:

• Create a samename Page Provider.
• Add a predicate to it bound to dc:title.
• Create a samename Schema (id and prefix). No fields need to be added.
• Create a documenttype Document Type. Add the samename schema to it.

In Designer:

• Configure the create layout of the documenttype Document Type. Notice that errors are displayed immediately regarding the field dublincore_title not being found in the schemas, and a Dublincore Title field was scaffolded as well (regarding the page provider predicate).

This seems to be caused by the schema that is generated for the page provider, whenever there are predicates/aggregates.

Workaround: renaming either the Schema or the Page Provider feature.