Unfortunately we're using `django-redis` to cache some `attrs` instances
and the change to make `__getstate__` and `__setstate__` use `dict`
values instead of `tuple` values prevents reading any values from the
cache when updating to `attrs>=22.2.0`. We get an `AttributeError`
raised for all attributes.

This happens because the tuple of values stored in the original pickle
is checked for the name of the attribute and so none of the attributes
are set on unpickle.

To address this I've made a change so that `__setstate__` will still be
able to handle values pickled as `tuple`s allowing existing pickles to
be unpickled.

The test just contains a pre-pickled value due to the complexities
around tying to mock methods on a slotted as documented[^1].

I realise that documentation also mentions that we should "think twice"
before using pickle, but sometimes those decisions predate our
involvement in a project! In addition, pretty much all of Django's cache
implementations are built around using pickle by default. This change
will allow an easier path to upgrade by unpickling and repickling all
values in the cache.

Regression in 89a890a.

[^1]: https://www.attrs.org/en/latest/glossary.html#term-slotted-classes