Fix missing slot false positives for finalize.atexit & TarInfo.path

[zyv]

Both are declared as bare instance attributes on classes whose stub also declares __slots__ without them, so type checkers reject every assignment to them even though the runtime allows it. CPython implements both as read-write properties.

weakref.finalize (Lib/weakref.py) has __slots__ = () and implements atexit as a property with a setter; the neighbouring alive is already modelled as a property in typeshed.

tarfile.TarInfo (Lib/tarfile.py) implements path as a read-write property aliasing name, exactly like linkpath aliases linkname; linkpath is already modelled as a property, path was not, and path is absent from the __slots__ tuple.

Reproducer, rejected before and accepted after this patch:

import tarfile
import weakref

class C: ...

def f(c: C, ti: tarfile.TarInfo) -> None:
    weakref.finalize(c, print).atexit = False
    ti.path = "x"

mypy 2.3.1 before:

error: Trying to assign name "atexit" that is not in "__slots__" of type "weakref.finalize"  [misc]
error: Trying to assign name "path" that is not in "__slots__" of type "tarfile.TarInfo"  [misc]

ty 0.0.77 reports the same two as missing-slot; pyrefly reports missing-attribute. stubtest output is unchanged for both modules.

The __slots__ entries came from the automated sweep in #14611 (part of #8832). The attribute declarations predate it, so the contradiction was introduced by adding __slots__ on top of them rather than by the annotations themselves.

[github-actions]

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

dd-trace-py (https://github.com/DataDog/dd-trace-py)
- ddtrace/internal/wrapping/context.py:485: error: Trying to assign name "atexit" that is not in "__slots__" of type "weakref.finalize"  [misc]

[srittau]

Thanks!