Support properties with generic setters

[ilevkivskyi]

This is yet another followup for checkmember work.

This handles a niche use case, but it is still used in the wild, and this restores parity between logic for descriptors with __set__() and properties with custom setters.

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

xarray (https://github.com/pydata/xarray)
- xarray/core/variable.py: note: In member "data" of class "Variable":
- xarray/core/variable.py:442: error: Incompatible override of a setter type  [override]
- xarray/core/variable.py:442: note:  (base class "NamedArray" defined the type as "_arrayfunction[Any, Any] | _arrayapi[Any, Any]",
- xarray/core/variable.py:442: note:  override has type "T_DuckArray | Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | complex | str | _NestedSequence[complex | bytes | str]")