Bug in nested QuerySet when defined via `objects = CustomManager(...)`

In continuation to https://github.com/tortoise/tortoise-orm/issues/864

Now it works if manager is defined like this:

class ManagerModel(AbstractManagerModel):
    class Meta:
        manager = StatusManager(queryset_cls=StatusQuerySet)

(Thats from tests/testmodels.py)

However it will not work if manager is defined like this:

class ManagerModel(AbstractManagerModel):
    objects = StatusManager(queryset_cls=StatusQuerySet)

However it works, when in tortoise/queryset.py:321

- queryset = self.__class__.__new__(QuerySet)
+ queryset = self.__class__.__new__(self.__class__)

Start with the ManagerModel definitions in tests/testmodels.py and inspect tortoise/queryset.py around line 321. Reproduce the difference between defining StatusManager through Meta.manager and objects, then verify that the objects form preserves the StatusQuerySet behavior shown in the issue.