operations.all.enabled(false) should only disable the provided operations, not user defined custom operations

This is what was really implied in grails/grails-data-graphql#37.

Since this is now already public and possibly in use, I'd suggest a `operations.provided.enabled` which specifically prevents the generation of the get/list/count/create/update/delete queries only.

Start by reading the behavior referenced in grails/grails-data-graphql#37 and tracing the configuration entry point for operations.all.enabled(false). Determine how provided operations are separated from user-defined custom operations; done means a new operations.provided.enabled setting disables only get/list/count/create/update/delete generation while custom operations remain available.

Written by the indexing model from the issue text.