Prevent `ContentType.objects.get_for_model` from creating objects for deferred, auto_created and swapped models

[ILYA]

This ticket is extracted from #23444 for the sake of clarity. See initial discussion there.

Briefly:

ContentType.objects.get_for_model method returns appropriate ContentType object for the model if it exsits and creates one if not. But it doesn't check whether a model passed to it is deferred, auto_created or swapped.
Thus we get unnecessary ContentType objects in our DB that will be removed after next sync_db/migrate as django by default considers such CT objects as stale (and doesn't create them by itself anyway).

[Simon Charette]

Additional checks could added for the auto_created and swapped cases but the deferred one ​seems to be already correctly handled?

[ILYA]

Yeah, seems like that.

So we have get_for_model and get_for_models mathod that need to be patched.
Checks for swapped and auto_created attrs are quite trivial but the question is what should we do in that case?
Should we raise an exception (e.g. ValueError as we get wrong model value) or simply return None to show that this model should not have CT object.
In the latter case I think we need also some docs notes for that.

Also we can consider whether we need some additional attrs for get_for_model so that it would create CT for swapped and auto_created models.

[Tim Graham]

Raising an error seems more explicit.