[red-knot] Initial set of descriptor protocol tests (#15972)
## Summary
This is a first step towards creating a test suite for
[descriptors](https://docs.python.org/3/howto/descriptor.html). It does
not (yet) aim to be exhaustive.
relevant ticket: #15966
## Test Plan
Compared desired behavior with the runtime behavior and the behavior of
existing type checkers.
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Co-authored-by: Mike Perlov <mishamsk@gmail.com>
