Allow composite entities to opt out of creating duplicate revisions
requested to merge issue/entity_reference_revisions-3267490:3267490-allow-composite-entities into 8.x-1.x
This pull request re-writes the existing code and introduces a policy chain which decides on whether a new revision should be created. This would enable other modules to override the existing hard coded business logic present in entity_reference_revisions module with there own custom business logic for revision creation.