Allow other modules to display permissions on the content type's Permissions tab

[herbdool]

Description of the need

Right now the list of permissions is only provided by core's node module. If a contrib (or other core) module has content type specific permissions, it would be user-friendly to also be able to display them on the content type form in the Permissions tab.

It would look like this where the last two permissions are provided by a custom module calling a hook:

[herbdool]

I've got a fairly focused PR that adds a hook. Core isn't using the hook currently.