Deleting a field or fieldable entity should remove the cm document if it exists

Problem/Motivation

When removing a field or endity, any content model documents persist even though they document something that no longer exists.

Ideally, when deleting a field or a fieldable entity, any content model document(s) for that item should be deleted as part of that operation.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes